322 UNITED STATES GEOLOGICAL SURVEY OF TOE TERRITORIES. 



say that, although he used the name Aporrhais, he applied it to Pterocera. 

 Dr. Stoliczka cites Petiver (1711) as the author of this genus; but, as both 

 he and Aldrovandi (17 78) did not conform to the binomial system of nomen- 

 clature, neither of them ought to be cited as the founders of genera; and the 

 same may also be said of Klein, who used this name apparently for a Strom- 

 bus in 1 753. It is, therefore, Dillwyn, who first used the name Aporrhais in a 

 regular binomial sense in 1823, that we must regard as the founder of the same 

 So far as is at present known, the genus Aporrhais seems not to date 

 back farther than the Cretaceous period, during which it was represented by 

 only a very few species, so far as our knowledge now extends. The Jurassic 

 shells that have been referred to it by some, belong to Alaria, Morris and 

 Lycett, Dkroloma, Gabb, and perhaps other groups ; while most of those 

 from the Cretaceous belong to Anchura, Helicaulax, and other allied types. 

 A single species hereinafter described from the Cretaceous seems to me to 

 have all the essential characters of the typical section of this genus. There 

 are also a few forms in the Cretaceous, and, as already intimated, in the Ter- 

 tiary, that closely approach the group Arrhoges, but may possibly be distinct. 

 The typical section is also represented in the Tertiaries, and, like the section 

 Arrhoges, in our existing seas. The living species of the former occur on 

 the English coast and in the Mediterranean ; while the existing typical spe- 

 cies of Arrhoges is found on the northeastern coast of the United States, on 

 the Banks of Newfoundland, Labrador, &c. 



Aporrhais biangulata, M. & H. 



Plate 19, figs. 6, a, b, c. 



Sostellaria biangulata, Meek and Hayden (1856), Proceed. Acad. Nat. Sci. Philad., VIII, 65. 

 ApoPrhais biangulata, Meek and Hayden (1860), ib., XII, 186. 



F 'g- 37 - Shell rather small, of nearly typical form ; 



spire acutely elevated ; volutions about eight, mod- 

 erately convex; suture distinct; last turn promi- 

 nent and biangular around the middle, the angles 

 or carinae being near each other, with a vertical, flat- 

 tened, or slightly concave space between, while the 



Aporrhais biangulata. . _ 



A magnified outline from a upper side is flattened with an outward slope Irom 

 specimen showing that it has t i ie su t ure to the upper angle, and the lower 



the usual posterior canal ascend- 

 ing the spire, abruptly contracted to the rather short, pointed, 



and nearly straight beak; outer lip forming a broad biangular expansion, 



