BRACHIOPODA. 
159 
It ought, perhaps, to be observed that in a postscript note circulated with 
some copies of the Twelfth Report on the New York State Museum of Natural 
History, the name Orthonom^a was proposed as a generic designation for 
Orthis ? erratica. Should it become desirable to distinguish these finely striated 
species from the more typical coarsely plicated Zygospira and the biconvex 
Catazyga, this term would be entitled to consideration. 
Genus CLINTONELLA. gen. nov. 
PLATE Lll. 
Diagnosis. Shells usually small, suboval in outline; valves subequally 
biconvex, the axis of greatest convexity being oblique, making an angle of 
about 55° with the vertical axis of the shell. Pedicle-valve with a small 
umbo, which is compressed laterally, the apex being slightly incurved. The 
cardinal area is replaced by a wide triangular delthyrium, which is unaccom¬ 
panied by any trace of deltidial plates. The medially elevated umbo merges 
anteriorly into a sinus which makes a deep flexure at the margin; it bears two 
plications, both of which reach the beak; sometimes a trace of a third plication 
may be seen. The lateral slopes bear from four to eight radial plications of 
smaller size. 
On the interior the teeth are prominent, strongly recurved at their tips and 
supported by lamellas which terminate abruptly. The lower and inner mar¬ 
gins of these lamellae are thickened, contracting the pedicle cavity, which is, 
consequently, narrow and deep. The diductor scars are of moderate size, 
flabellate in outline and deeply impressed at their posterior extremity. They 
Anticostiensis and borealis “are only variations in shape of the same species, but specifically distinct 
from the Zygospira (Athyris ?) Headi of Billings.” Further, in indicating the differences between A. Headi 
and A. Anticostiemis, he says : “ the most marked external characters consist in Afeadi having in the dorsal 
valve a somewhat deep longitudinal depression or sinus, while, on the contrary, Anticostiensis has the sinus 
on the ventral valve.” On the preceding page, in treating of Z. erratica, the author says: “ Z. em'atica also 
bears some resemblance to Z. Headi in its external form, especially as in both species there is a somewhat 
deep sinus in the dorsal valve.” It seems probable from these statements that Mr. Davidson has confounded 
the typical A. Headi with the variety A. Anticostiensis, and this supposition is apparently borne out by the 
assertion that the Rev. Mr. Glass succeeded in develojiing the brachial apparatus in Z. erratica. This 
species, as far as we know, is invariably preserved as sandstone casts or in a matrix of sandstone, and to 
develop its internal apparatus has proven an impossibility. The specimens of Z. Anticostiensis are, how¬ 
ever, usually in limestone, and are very favorable subjects for such treatment. 
