Transactions of the Linnean Society of London/Volume 12/Descriptions of five British Species of the Genus Terebella of Linné

XIX. Descriptions of five British Species of the Genus Terebella of Linné. By the late George Montagu, Esq. F.L.S. Communicated by William Elford Leach, M.D. F.R.S. and L.S.

Read March 4, 1817.

TEREBELLA.

Gen. Char.Body long and annulated, furnished on each side with pedunculated feet terminated with bristles, which are retractile: head with numerous long simple capillary appendages: three small ramified branchiæ on each side behind the head.
The animals of this genus either prepare a sheath from the tenacious secretion of their bodies mixed with adventitious matter, or reside in prepared perforations at the bottom of the sea. The tubes which are prepared by them are in general so extremely delicate, that they are very easily destroyed, and they are then found lurking beneath stones, or forming a new habitation by connecting together sand or mud with the slimy secretion of their bodies. Some species form a tube in old shells or stones, to which they adhere by the whole length; others fix a tube perpendicularly in the sand, with two or three inches projecting above the surface. Many are gregarious, and so numerous, that we have seen the shore covered with the fragments of their tubes after a storm: thus, from the fragility of their tubes, these animals are often found at large. When in their tubes, generally but a small part is protruded, excepting the capillary tentacula, with which they seem to be searching for food in every direction by thrusting them into cavities of shells, under stones, &c.

The branchial appendages are usually coloured with orange or red whilst the animals are alive and in health, but lose their colour as they become weak or sickly, which probably arises from languid circulation.

The mouth is in front, and the under-lip usually projects so as to make the opening upwards.

All the species inhabit the sea.

Spec. 1.Terebella gigantea.

Tab. XI.

T. with seventeen pairs of exserted fasciculi and eight dorsal plates.

Body long, with numerous articulations furnished the whole length with peduncles, and a few with fasciculate bristles; but the seventeen anterior joints have the fasciculi most conspicuous, being always erected, and remaining so after death: the first eight joints have a broad plate on the back different in structure from the rest; they are of a rufous-brown colour, shaded with purplish-black, continuing down the back in a decreasing line. The general colour of the other parts is yellowish. Beyond the seventeen first joints the peduncles are very small, and appear to be destitute of fasciculi; and they incline gradually from the sides to the back, till towards the extremity they almost meet, forming two dorsal lines: near the mouth originate numerous capillary appendages, that are five or six inches in length: the three pair of branchiæ are much ramified, and red.

Length sixteen inches.

Inhabits the Devon coast, but is very rare.

T. gigantea is the largest of the discovered species; it inhabits the soil at the bottom of the sea, and seems to be destitute of any case. We found one specimen in the estuary of Kingsbridge at low water: it discharged an orange-coloured fluid from its mouth in great abundance.

 

Spec. 2.Terebella cirrhata.
Tab. XII. Fig. 1.

T. with eleven oval dorsal plates on the anterior articulations.

Body long, with numerous orange-coloured articulations, furnished with small peduncles, and at the anterior end with fasciculi of bristles: branchiæ large and red: mouth with a frill-like membrane beneath, and ciliated above. Capillary appendages four or five inches in length.

Length nearly twelve inches.

Diameter near the head half an inch.

The tube (which is described in Testacea Britannica under the name Sabella cirrhata) is very fragile; it is composed of sand and clay, and is lodged in the ground, with half an inch projecting above the surface.

This species is gregarious, and is not uncommon on the southern coast of Devon.

Spec. 3.Terebella nebulosa.
Tab. XII. Fig. 2.

T. with its body spotted with white, having thirteen dorsal plates.

Body long, orange-red, spotted all over with white. Anterior extremity very tumid, defended by the dorsal plates: anterior peduncles very small, with the fasciculi pointed. The other peduncles and fasciculi are broad. The posterior end is abruptly smaller than the other, as if it had been lost by accident, and afterwards reproduced. The capillary tentacula are numerous, and of a pale orange-colour spotted with white. Branchiæ red with white spots.

Length six or seven inches.

Diameter of the largest part half an inch.

Inhabits the southern coast of Devon rarely, being taken only by deep dredging. Its case is composed of slimy matter, covered with gravel and broken shells.

Spec. 4.Terebella Constrictor.
Tab. XIII. Fig. 1.

T. with twelve broad plates on the back: capillary appendages pale.

Body orange-red, with about one hundred and twenty approximate articulations furnished with small fasciculi; those behind the dorsal plates are divided down the middle by a sulcus: mouth with an expanded lower lip, surrounded with capillary appendages longer than the body.

Length three or four inches.

Inhabits the coast of Devon, and is rare.

The very closely-connected articulations discriminate this species from any of the others. Its case or tube is unknown.

Spec. 5.Terebella venustula.
Tab. XIII. Fig. 2.

T. with orange-red body, thickly and minutely marked with white spots.

First seventeen or eighteen joints furnished with short peduncles and fasciculi: other joints with long peduncles and no visible bristles. Capillary appendages whitish, very slender, numerous, and nearly double the length of the body. We have observed this animal fixing its tentacula, and by contracting them drawing its body forwards.

Length rarely more than three or four inches.

Taken by dredging on the southern coast of Devon at Torcross.