CONTRIBUTIONS TO PALEONTOLOGY. 41 



In September 1862, Prof. A. Winchell, in his ''Description of 

 Fossils from the Marshall and Huron groups of Michigan ^^'' published 

 a description of Centronella julia^ in which he describes the loop, 

 which proves to be very distinct from that of Centronella as 

 described and illustrated in the Canadian Maturalist and Geologist, 

 Vol.iv, April 1859. 



Through the kindness of Prof. Winchell, I have been put in 

 possession of some specimens of this species, with parts of others 

 illustrating the internal structure, together with drawings re- 

 presenting the loop. 



An examination of the external characters shows that the shell 

 has the form and texture of Cryptonella : " Both valves with 

 regular lens-like convexity, shell obsoletely striate concentrically, 

 and having a minutely punctate structure.'' The form and other 

 characters of the cast are like that of species referred by me to 

 Cryptonella. In the ventral valve are two delicate, slightly 

 curving dental lamellae, which are shown in casts by a narrow slit 

 on each side of the beak. " The casts exhibit on the ventral side 

 a delicate impressed line extending from the beak to the middle, 

 and on the right and left of this a fainter one ; on the dorsal side, a 

 median impression, with two fainter ones on the right and two on 

 the left." These characters appertain to the casts of Cryptonella 

 (See figs. 6 & 9), as shown in the ventral side of large individuals; 

 having three defined, slightly impressed spaces, limited by narrow 

 lines which extend to the middle of the shell, below which there 

 are sometimes vascular impressions visible. 



On the dorsal side we have the median impressed line with two 

 fainter ones on each side, which, in some conditions of preserva- 

 tion, are obscured by the muscular impression ; and below these 

 are frequently seen diverging vascular impressions. 



The internal loop of Cryptonella julia, illustrated from drawings 

 of Prof. Winchell, is shown in figures 1 and 2, which are four 

 times enlarged, and are thus described by him : " A delicate 

 ribbon-like loop originates from the stout blunt crura on each side 

 of the socket-valve, having its flat sides at first vertical : the two 

 branches of the loop proceed at first in lines parallel or a little 

 convergent, and then gradually diverge, widening as they proceed, 

 and assuming an inclined position, until, approaching the front 



STELLA in 18G0 ( Thirteenth Report on the State Cabinet, page 84), and a part under 

 TeA'^.bratula, from the characters of which I proposed the Genus Cryptonella in 

 1861. The former belong to the Spiriferid^, and the latter to the Terebratulid-«!. 



[Senate, No. 115.] 6 



