NATURAL SCIENCES OP PHILADELPHIA. 123 



Brach. pi. xxiii. iig. 19-21.) The ribs, however, are more numerous, and the 

 frontal commissure more deeply sinuate. 



CENTRONELLA, Billings. 



Centronella Allei, n. sp. Shell large to medium size, terebratuliform, 

 greatest width a little anterior to the middle, contained one and one fourth 

 times in the greatest length. Ventral valve somewhat ventricose, full to the 

 immediate vicinity of the margin, especially along the cardinal slopes ; regu- 

 larly arching from beak to anterior margin, highest in the middle ; anterior 

 margin with a barely perceptible truncation ; no -sinus or fold present ; beak 

 produced beyond that of the dorsal valve, truncated and circularly perforate 

 at the extremity ; dental lamellae more than one-fifth the whole length of the 

 valve ; muscular scars, consisting of one faint median linear impression, on 

 each side of which is another, all reaching to the middle of the valve. Dor- 

 sal valve with its short imperforate beak closely concealed under that of its 

 fellow, slightly truncate in front, but without mesial fold or sinus ; regularly 

 arched from beak to front, highest in the middle, exhibiting a convexity 

 equal to that of the opposite valve. Muscular scars consisting of a faint but 

 distinct linear median impression, with a much deeper linear impression on 

 each side, and a very faint one exterior to each of these the three principal 

 impressions reaching to the middle of the valve. Shell thin, stony and solid ; 

 structure beautifully punctate under a lens ; general surface polished, mark- 

 ed by a few feeble concentric lines of growth. 



Length of ventral valve, -66 (100) ; breadth, -41 (62) ; convexity, -19 (29). 



The dorsal valve above referred to comes from bed " No. b'," at Burlington; 

 the other specimens are apparently from "No. 5." " White collection " of 

 the University of Michigan. Also near Hamburg, Illinois, and at Talmadge, 

 Summit county, Ohio. Whittlesey's collection. 



Though the peculiar loop of Centronella has not been seen in these speci- 

 mens, the characters given are so closely conformable with that genus that 

 the reference can scarcely be questioned in the present state of our knowledge. 

 It is a larger, more ventricose and more elongated shell than C. Julia. 



Centronella Julia, Win. A single small specimen of this northern spe- 

 cies occurs in Whittlesey's Collection, from "one mile east of Orange Center, 

 Cuyahoga county, Ohio." 



Specimens of this species from Pt. aux Barques, have been employed by 

 Prof. Hall to illustrate the characters of his genus Cryptonella, (Trans. Albany 

 Inst. Feb. 3, 18(53, p. 4 ; reprinted Amer. Jour. Sci. [2] xxav. 399. J The re- 

 ference of this species to Centronella was made solely in the light of Billings 7 

 description and figure of that genus and comparisons with the internal struc- 

 ture of Centronella glansfagea, the type of the genus. Prof. Hall asserts that 

 the description and figure do not bear out the reference ; and, having pre- 

 viously founded Cryptonella on the external characters of certain terebratuli- 

 form species, he assumes that Centronella Julia affords an exhibition of the 

 internal characters of Cryptonella. There is not the least doubt that the ori- 

 ginal reference of Centronella Julia was correct ; and since its internal char- 

 acters are assumed by Prof. Hall as being those of Cryptonella, the latter 

 genus is thus admitted by its author to cover the same ground as the older 

 genus Centronella, and must consequently pass out of use. Prof. Hall seems to 

 have suspected this result ; for in a note interpolated in the New Haven edition 

 of his paper, (p. 405,) he refers to a drawing of a specimen of C. glansfagea, 

 showing the loop, (sent him by Dr. Rominger of Ann Arbor,) and admits that 

 the loop " shows essentially the same character as that of Cryptonella.'''' He yet 

 insists that this character is not to be inferred from Billings' original descrip- 

 tion and figure ; and, expressing a doubt about the identity of Billings' type 

 species (C. glansfagea) and the one figured by Rominger, "hesitates to 



1865.] 



