128 



In September, 1862, Prof. A. Winchell, in his " Descrip- 

 tions of fossils from the Marshall and Huron Groups, of Michi- 

 gan" published a description of Centronella julia, in which 

 he describes the loop, which is proved not to be in accord- 

 was written, I have ascertained the generic characters of the so-called Atrypa 

 or Athyris scitula. It has internal spires with their apices directed outwards, 

 as in Athyris and Spirigcra, hut the dorsal hinge-plate has its anterior margin 

 and a large portion along the middle rnchylosed to the bottom of the valve. 

 In another congeneric species, the middle portion of the same plate is obsolete, 

 there remaining only two small, thin, nearly vertical septa (socket plates), one 

 on each side of the cavity of the umbo. The perforation in the beak of the 

 ventral valve is bounded on the lower side by a deltidium of either one or 

 two pieces, or by a portion of the shell. The mesial septum in the dorsal 

 valve is either rudimentary or eutirely absent. 



" The several species of this group, at present known to me, resemble 

 Athyris, but are not so convex, and are besides more elongate ovate, or ap- 

 proaching to Terebratula in general form. I shall give further details and 

 some figures in the next number of the Journal." 



" The genus is only proposed as a sub-genus to be retained in case Athyris 

 is divided." 



In the Canadian Journal, No. xxxui, p. 273, we have " Charionella Circe, 

 N. Sp." (referring to the illustrations). " The first figure exhibits a specimen 

 with the dorsal valve partly removed, showing the internal spires. The other 

 two figures are a side and ventral view of another specimen." 



" By treating partially silicified specimens of this genus with acids, I have 

 ascertained that the structure of the hinge plate differs from that of Spirigera 

 in being either obsolete along the middle or anchylosed to the bottom of the 

 valve. In Athyris (=Meristella, Hall) there is a well developed hinge plate, 

 supported beneath by a strong mesial septum, which extends sometimes 

 nearly to the front of the valve. In Charionella there is either no mesial sep- 

 tum, or one that is merely rudimentary. In one specimen there is a remark- 

 able partition, which runs obliquely from near the beak to the margin near 

 the front. It completely divides the internal cavity into two parts. This I 

 believe to be not a mesial septum, but a temporary wall formed by disease of 

 the animal, because both spires are crowded into the smaller of the two cavities, the 

 larger being empty." 



The genus Charionella, therefore, clearly belongs to the Spiriferidce, and the 

 typical species cited are, in part those originally placed by me under the 

 genus Meristella, in 1860 (Thirteenth Report on the State Cabinet, p. 84), 

 and a part under Terebratula, from the characters of which I proposed the 

 genus Cryptonella in 1861. The former belong to the Spiriferidce, and th« 

 latter to the Terebratulidce. 



