148 PROCEEDINGS OP THE ACADEMY OF 



leaving some doubts in regard to the presence of the fasciale characteristics of 

 that genus. The posterior position of the apical disc, and the close proximity 

 of mouth to the front, as well as the great inequality of the posterior and anterior 

 lateral ambulacra, appear to remove it from the genus Toxaster. In some re- 

 spects it resembles the genus Schizaster, but does not decline so distinctly to- 

 wards the front above, as is common amongst the species of that genus. It may 

 belong to a new type. 



It is remarkable, that in all the collections hitherto obtaiued from the 

 Cretaceous rocks of Nebraska, this is the only species of Echinodi-nn yet 

 met with, and it is so rare that but the single specimen now before us, and a 

 fragment mentioned in one of our former papers, from the same locality, have 

 been met with. 



We take pleasure in naming this rare and beautiful fossil in honor of 

 Capt. A. A. Humphreys, of the U. S. Topographical Engineers. 



Locality and position. Yellow Stone River, in a bed composed of a blending 

 of No. 4 and 5 of the general section. 



On the LABVA of the Thyreus Abbottii. 

 BY J. P. KIRTLAND, M. D. 



Swainson, in his Zoological Illustrations, vol. i. First Series, described the 

 Thyreus Abbottii, which, together with the Pupa and Larva, he figured on the 

 authority of Mr. Abbott's unpublished drawings. 



Dr. Harris' Catalogue of North American Sphinges, in the Amer. Jour, of 

 .Sciences and Arts, vol. xxxvi., contains also a description of this larva, drawn 

 from Swainson's sketch. With due deference to these high authorities, I beg 

 leave to state, that neither their figures nor descriptions bears the least re- 

 semblance to the true larva. 



During the last three years I have reared many of them and carried them 

 through the second stages of transformation to the perfect insect. 



At maturity the Larva is about the length of Swainson's figure, but its 

 diameter is one-fifth less. Its upper surface is ash color, with its belly and 

 legs tinged with a faint violet. It is not furnished with a caudal horn as repre- 

 sented in Swainson's figure, but in place of it has an oval eyelet or occuli, of a 

 glossy brown color, and a line or two in diameter. This Larva resembles more 

 the common silk worm (Bombyx mori) than it does Swainson's figure. Its 

 principal food is the leaf of the Ampelopsis quinquefolia, though it occasionally 

 is found on the cultivated grape vine. 



During the month of August it attains its full size, and individuals may be 

 seen at night descending to the ground, where it enters the pupae state, below 

 the reach of frost. 



Specimens kept in boxes of earth beneath the shelves of a warm green house, 

 appeared in the perfect state as early as the first of April, while those pre- 

 served in a cool cellar did not assume that form till late in May, or early in 

 June. 



That Dr. Harris was led into an error by Swainson's figure I have no doubt, 

 for Dr. H. sent me a drawing and colored figure of this true Larva four years 

 since, requesting of me information as to the perfect insect it produced. To 

 prevent a further extension of that error is the object of this communication. 



[May, 



