128 NEW-YORK FAUNA MOLLUSCA. 



(EXTRALIMITAL) 



Genus Pirena, Lamarck. Animal with an elongated rostrum: tentacles two, contractile, conic, 



annulated, with the eyes on peduncles at their external bases; foot short, oval, angular in 



front on each side ; breathing-hole in the furrow, formed by the union of the mouth with the 



body. Freshwater. Shell turreted ; aperture longitudinal. Lip acute, with a distinct sinus 



at the base, and another at its junction with the body : base of the columella turned towards 



the right. Opercle horny, subspiral. 



P. scalariformis. (Say, Ac. Sc. Vol. 5, p. 128.) Whorls rounded, with numerous elevated lines, ending 



the body-whorl by 5 - 6 revolving grooves : suture well impressed, with one of the grooves so near 



as to cause it to appear double ; aperture rounded ; lip thickened, somewhat recurved ; sinus slight 



at the base, more obtuse above. No umbilicus. Color, pale, with several revolving reddish lines. 



Length, 0-9. Florida Keys. 



FAMILY CERITHIDJE. 



Animal with an elongated rostrum, without a trunk, but surmounted by a veil. Tentacles 

 with the eyes about their middle, and externally. Inhabiting salt water. Shell elongated, 

 with the aperture much shorter than the remainder of its length. Opercle horny. 



Obs. This comprises a portion of the family Canalifera of Lamarck. 



GENUS CERITHIUM. Adanson. 



Animal elongated, spiral, with its rostrum depressed, and covered by a veil which is often 

 fringed. Tentacles distant, annulated, and bearing the eyes on a protuberance near the 

 middle. Mouth without teeth, but with a small tongue. Foot short, oval, with a marginal 

 furrow in front. Mantle forming on the left side a canal, or the rudiment of a syphon. 

 Branchial cavity with a single gill, which is long and narrow. Shell turreted, elongated, 

 almost always tuberculated. Aperture short, oval, oblique, with a short recurved often 

 truncated canal. 



Cerithium sayi. 



PLATE VIII. FIG. 167. 



(STATE COLLECTION.) 



Pasithca nigra. Totten, Am. Jour. Sc. Vol 26, p. 369, pi. 1, fig. 7. (Young.) 



Ccriihiumreticulatum. Id. lb Vol. 28, p. 352, fig. 8. 



C. id. Adams, Bost. Journ. Nat. Hist. Vol. 2, p. 273. 



C. sayi. Gould, from Menke, Invertebrata of Mass. p. 278, fig. 183. 



Description. Shell small, acute, conic, thin. Whorls from six to eight, flat, with a dis- 

 tinct shoulder, formed by a series of granules. Surface granular, from the crossing of slightly 



