Organs of Locomotion. Fins two; dorsal one large, rounded, moved by twenty pair of compressed muscles, each terminating in a bifurcated point, and united in that part of the opposite muscle, confluent at base, and furnished with two radicles, which penetrate the body between the peritoneum and the exterior gelatinous substance. Caudal fin very small, lobated or rounded, including small ramose vessels, and moved by three pairs of muscles, at their extremities filiform and united in a common point. I have not been able to perceive any distinct muscles in other parts of the body, excepting those already mentioned, and numerous oblique ones between the peritoneum and the gelatinous exterior.
Amongst a great number of individuals which I have examined, the number and situation of the organs or appendages, and presence or absence of either of them, have furnished me with good specific characters. Of these I have availed myself to establish the following fix species.
1. F. mutica. No vermiform organ; no cup on the dorsal fin; no caudal appendage. Plate I. fig. 1.
Substance firm, diaphanous, tuberculated, rosaceous; tubercles irregularly placed, and of a deeper colour. Dorsal fin near the nucleus, placed in a groove. Trunk wrinkled, and with the region of the dorsal fin spotted with white. Gelatinous points six, disposed by opposite pairs in two longitudinal lines.
2. F. gibbosa. Body furnished with a vermiform organ; no cup or caudal appendage. Plate I. fig. 2.
Body gibbose above the nucleus, narrowed behind the eyes, and emarginate at the base of the dorsal fin.
