324 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



Genus ANCHURA, Conrad. 



Synon. — Anchura, Conrad (1860), Jour. Acad. Nat. Sci , IV (2d ser.), 284 ; and (1873) in Appendix to Kerr's 

 N. Car. Geol. Rep., 12. — Meek (1864), Smithsonian Check-List N. Am. Cret. Fossils, 

 19.— Gabb (1868), Am. Jour. Conch., IV, 145; and (1869) Palseont. Cal., II, 165.— 

 Stoliczka (1868),Palseont. Indica, II, '26.— Dana (1874), Man. Geol. (2d ed.), 461. 

 Drepanochdus, Meek (1864), Smithsonian Cheek-List N. Am. Cret. Fossils, 19 and 35 (proposed 

 as a subgenus under Anchura). — Dana (1874), Man. Geol. (2d ed.), 461 (retained as a 

 subgenus under Anchura). 

 Perissoptera, Tate ( 1865), Geol. and Nat. Hist. Repertory, Lond. 



Etijm. — ayxL, near; oi-pa, a tail ; from the tail-like appearance of the beak of the type-species. 

 Type.— Anchura ahruptc*, Conrad. 



Shell, exclusive of the extended lip, fusiform ; beak slender, more or less 

 produced, pointed,' and straight, or very slightly rlexuous ; outer lip at matu- 

 rity narrow, more or less sinuous below, and extended either into two unequal 

 pointed digitations, directed one anteriorly, and the other posteriorly, or ter- 

 minating in a single backwardly curved, scythe-shaped process ; inner lip 

 callous; aperture without a posterior canal. 



In this genus, I admit the following two not very strongly-deferent sec- 

 tions: 



1. anchura, Conrad (typical). 



Shell with outer lip terminating in two unequal pointed processes, 

 one directed backward and the other forward ; beak typically very 

 long and slender. — (Type as above given.) 



2. drepanochilus, Meek (=: Perissoptera, Tate, in part). 



Shell with outer lip terminating in a single backwardly-curved, 

 scythe-shaped, pointed process; beak short. — (Rostellaria Americana 

 Evans and Shumard.) 



As elsewhere stated, this genus is distinguished from Aporrhais by being 

 entirely without any traces of a posterior canal* ascending the spire, as well 

 as by the different forms of its expanded lip. The beak of the species belong- 

 ing to the typical section is also much longer and more slender than in 

 Aporrhais. It is more nearly related to Dicroloma, Gabb, which also has no 

 posterior canal, and seems to differ chiefly in its much inore deeply bifid 

 outer lip and curved canal. 



The genus Anchura is probably mainly, if not entirely, confined to the 

 Cretaceous rocks. It is certainly unknown in the Tertiaries, and among 

 existing mollusks. Some of the Jurassic shells, however, seem to approach 

 it pretty nearly, and may not be generically distinct. 



