with powerful propelling flippers. The preceding cut illustrates its form and size in relation to the posterior dorsals from nearly the same position in the C. magnus and Elasmosaurus platyurus.
The general characters of the cervical and dorsal series are very similar to those of Elasmosaurus, but they all exhibit considerably larger neural canals. In the immature individual, the neural arch of the dorsal vertebræ is not coössified, but is separated by suture as in Plesiosaurus.
That there are several species of this genus is suggested by Leidy, and seems probable to the writer. As one of these has been already named, the characters of those which appear distinct may be pointed out.
Anterior caudals, articular faces with rounded margins ; antero-posterior diameter greater, 2 in., width, 2 in. 7 1. Pit of diapophysis 1 in. 3 1.
Anterior caudals, articular faces with. acute marginal angle, antero-posteriorly shorter 1 in. 7 1. by 2 in. 6 1. in width ; pit 11 1. Cervical with straight sides and broader form ; width 31.2 1. by 24.5 long, the ?diapophysis narrow and stout.
Anterior dorsals shorter and higher than in C. magnus, the posterior cexvicals, therefore shorter than in the same ; diapophysis of first dorsal longer.
Posterior cervical with neural canal as large as C. magnus, but centrum four times as large, and a strong longitudinal ridge half way between plcurapophysis and neural arch, giving pentagonal section : 45 1. long by 52 1. wide ; hence longer.
CIMOLIASAURUS VETUSTUS, Leidy.
Discosaurus Leidy, Proc. Acad. N. Sci., 1851, 620. Cretaceous Reptiles, N. A., 22. Plesiosaurus, DeKay Ann. Lyc., N. Y., 1828, 165, Tab.
If the vertebræ from Alabama from Jos. Jones, described by Leidy in the Cretaceous Reptiles as No. 1, are typical of this species, they present certain peculiarities which distinguish them from those of an individual of C. magnus which I describe below ; perhaps the species are distinct.
Cretaceous Alabama, ?Mississippi and ?New Jersey.
