382 Scientific Proceedings of the 



Dr. W. also made some remarks upon a skeleton of the sloth {Brady' 

 pus tridactylus) prepared by himself. The following are some of the pe- 

 culiarities in its structure, viz. its three toes; its walking upon the side 

 of the foot; the divergence of the posterior extremities from the pelvis ; 

 the articulation of the fibula as well as of the tibia with the astragalus; 

 the length of the anterior extremities, so that the fore arm, as well as the 

 hand, is planted upon the ground in walking, so as to bring the body into 

 a horizontal position ; the extensive coossification which takes place in all 

 the bones of the hand and foot ; the peculiar lateral disposition of the 

 claws, and the source of the deception in President Jefferson's notions of 

 the Megalonyi, so philosophically and decisively controverted by Cuvier; 

 the bifurcation of the zygomatic process; and especially the existence of 

 nine cervical vertebrae instead of seven, as found in all other animals. 

 This last point, he observed, was still controverted, it being contended 

 that what appears to be a transverse process only, does in fact bear the 

 rudiment of a rib. Dr. W., however, has been unable to detect any thing 

 like an articulating surface in this specimen, an old one, by long macera- 

 tion of the bones. The eighth vertebra also has a distinct circular fora- 

 men for the vertebral artery, which is the distinctive character of the cer- 

 vical vertebrae. 



Dr. J. B. S. Jackson remarked, that in regard to the transverse process 

 bearing a rudimentary rib, something analogous was found in the human 

 foetus, the transverse process of the seventh cervical vertebra being a sep- 

 arate piece which afterwards becomes coossified. 



Dr. Storer stated, that he had received another letter from J. G. An- 

 thony, Esq., of Cincinnati, communicating the discovery of a new ge- 

 nus of the Trilobite family, and that he had submitted it to Mr. Tesche- 

 macher. 



June 20, 1838, — G. B. Emerson, Esq., President, in the chair. 



Joseph P. Couthouy, Esq., began the reading of a monograph of the 

 Family Osteodesmacea of Deshayes, embracing the genera Thracia, Ana- 

 tina, Periploma and Osteodes?7ia. He commenced with the genus Thra- 

 cia, and shewed the great confusion which now exists in respect to both 

 the generic and specific characters. This had arisen partly from British 

 writers having confounded the type of the genus, Anatina declivis, Pen- 

 nant, {Anatina myalls, Lam.) witli another species, BTya declivis, Donov. 

 {Anatina convexa, Turton,) and more especially by Blainville supposing 

 a shell before him to be Anat. myalis, which was not so, but was Anat, 

 trapezoides, and which he consequently removed from the genus Thracia 

 and made it the type of Osteodesma, which genus again, he erroneously 

 considers to be synonymous with Periploma, Schumacher. Hence have 

 originated numerous other mistakes in subsequent writers. He then en- 

 deavored at great length to reconcile the synonymy of the following spe- 

 cies, and the following are the results of his research. 



