60 



Samuel Kneeland, Jr., M. D., Comparative Anatomy. 



William Stimpson, Conclwlogy. 



Horatio R. Storer, Herpetology. 



Recording Secretary, 

 Samuel L. Abbot, M. D. 



Mr. Ayres described a new Holothurian recently received 

 by him from George's Bank, belonging to the genus Thy- 

 onidium, instituted by Duben and Koren to receive the 

 sp^ies with scattered but somewhat regular suckers, une- 

 qual tentacula, and divided genital tubes. The general 

 appearance of the present type may be inferred from the 

 name, Sea Caterpillar, given it by the fishermen. It is 

 proposed to call tlie species, T. eloiigatum. 



T. elongatum Ayres. Suckers scattered irregularly, but as 

 they are somewhat more numerous on the sides of the longitu- 

 dinal muscles, five rows can be indistinctly traced. No calcare- 

 ous deposits on the sides of the suckers, a very slight terminal 

 plate being their only support. Tentacula ten, ramose, of une- 

 qual development, five alternating with the other five, which are 

 scarcely half as large. The entire oral apparatus remarkably 

 small ; the largest tentacula in a specimen of four inches being 

 not more than a fourth of an inch long. Oral circle and pouch 

 of course corresponding. The tentacula, especially toward their 

 extremities, have strong calcareous supports, consisting of perfo- 

 rated, irregular plates, of larger relative size than in most gen- 

 era, but not so large as to render them rigid. The oral circle 

 resembles that of PsoZms, Botryodactyla, and Slereoderma. The 

 integuments, except in the suckers, present numerous long, very 

 slender spiculae, enlarged at the base and ribbed longitudinally, 

 but not perforated. Intestinal canal without muscular stomach, 

 simple, about three times the length of the animal. Respiratory 

 trees not largely developed. The genital tubes present a re- 

 markable feature among Holothuridse of this form, in being 

 divided into two or three branches. Most of them are single in 

 the greater part of their length, the division being near the 

 extremity. They are also peculiar in their position, being 



