69 



Dr. James Robbins of N. Chester, and Messrs. William 

 Vaux and John A. Clay were elected Corresponding Mem- 

 bers. 



June 18, I 85 I. 

 Dr. D. H. Storer, Vice-President, in the Chair. 



Mr. Ayres stated that he had recently received from 

 George's Bank, and obtained from fishes taken in the Bay, 

 several specimens of Holothuridae belonging to the genus 

 Thyonidium. They represent three species, two of which 

 are new. 



T. glahrum Ayres. Tentacula ten, ramose ; of unequal de- 

 velopment, three being about an inch long (in an individual of 

 seven inches,) three a little less, two shorter still, and two only a 

 third of an inch. They have strong calcareous supports, espe- 

 cially toward their extremities, closely resembling those of T. 

 elongaiiim. Oral circle similar to that of the species just named. 

 Suckers not numerous, scattered irregularly, though a tendency 

 to arrangement in five rows may be traced. They are destitute 

 of support, and in fact the species may be characterized by the 

 absence of all calcareous deposit except in the suckers and the 

 oral circle. Intestinal canal simple, without muscular stomach, 

 a little more than three times the length of the animal. Pyriform 

 sacs three, about an inch long. Respiratory trees largely de- 

 veloped, their length exceeding that of the entire animal when 

 most extended ; firmly attached to the walls of the body by 

 strong tendinous slips. Cloaca large, and its muscular threads 

 very numerous. Genital tubes in their point of origin, their 

 duct, and their divisions similar to those of elongatum. Longi- 

 tudinal muscles not of uncommon strength. Retractors inserted 

 further back on the divided parts of the oral circle than in many 

 species. 



The specimen was taken on George's Bank in about thirty 

 fathoms of water. 



