354 MOLLUSCA. MURICIDiE. Pleurotoma. 



25. F. pernvianus. — Subfusiform, ventricose, smooth, with fifteen thin cos- 

 tse ; beak a little recurved. — Murex per. Sower. Min. Conch, t. ccccxxxiv. 

 f. 1. — In Crag. 



26. F. alveolatus — Turrited; volutions ornamented with two spiral ob- 

 tuse carinae, crossed by thick ribs; beak half cylindrical, ribbed — Sower. 

 Min. Conch, t. ccccxxv. f. 1 — In Crag, Suffolk. 



27. F. cancellatus. — Lanceolate, acute, covered with acute decussating rid- 

 ges, with short spines at the points of their intersection ; whorls ventricose ; 

 aperture oblong, produced into a short beak. — Sotver. Min. Conch, t. ccccxxv. 

 f. 2.— In Crag. 



Gen. LXXX. PLEUROTOMA. — Shell turrited, canal 

 straight ; a gutter or notch at the junction of the outer-lip 

 with the body-whorl. 



— 349. P. gracilis. — Whorls ten ; ribs interrupted at the sepa- 

 rating line by a depressed spirally striated space; canal pro- 

 duced. 



Murex gracilis, Mont. Test. Brit. 267- t. xv. £ 5— M. emarginatus, 

 Don. Brit. Shells, t. clxix. f. 2 In deep water, not common. 



Length an inch, breadth a quarter ; yellowish-white, with light coloured 

 and brown bands ; whorls tapering, little rounded, with numerous obtuse 

 longitudinal ribs, crossed by well defined spiral striae ; aperture ovate, the 

 outer-lip slightly crenulated by the spiral striae ; canal rather open, but pro- 

 duced in consequence of the bending in of the outer-lip, giving to the base 

 an acuminated aspect. 



350. P. sinuosa. — Whorls six, longitudinal ribs slightly 



interrupted by a depressed space at the separating line. 



Murex sin. Mont. Test. Brit. 264. t. ix. f. 8 — In deep water, rare. 



Length f ths of an inch, breadth a quarter, white, strong ; whorls slightly 

 compressed, and a little flattened at the top of each ; ribs numerous, ele- 

 vated, bent at the angle of the flattened space, and diminishing towards the 

 separating line : regularly striated spirally ; aperture oblong, oval ; canal 

 open ; very short, in consequence of the outer-lip continuing entire ; the 

 base has a blunt aspect. In a specimen which I found in Zetland, the spiral 

 strise are strong, giving the shell a coarsely reticulated appearance. 



EXTINCT SPECIES. 



1. P. attenuata Fusiform, base attenuated ; longitudinally undulated; un- 

 dulations five or six, with a large compressed tubercle at the upper end oi 

 each ; volutions transversely striated ; aperture narrow 1 , straight — Sower. 

 Min. Conch, t. cxlvi. f. 1 — London Clay. 



2. P. exorta.—. Turrited, base conical, elongated; whorls concave and 

 smooth above, below, longitudinally undulated and convex, with many ele- 

 vated subtuberculate dlines ; aperture ovate, elongated, canaliculated.) — Mu- 

 rex exortus, Brander, f. 32.— (Sower. Min. Conch, t. cxvi, f. 2.) — London Clay. 



3. P. rostrata Fusiform, with many transverse ridges and short costse, 



volutions obscurely decussated, expanded, and slightly concave above, rather 

 ventricose and roughish below : aperture elongated, canaliculated. — (Murex 

 ros. Brander, f. 34.) — Sower. Min. Conch, t. clxvi, f. 3 — London Clay. 



