326 MALACOZOA. GASTEROPODA. PECTINIBBANCHIATA. 



the mouth white, but not pearly, and a white worn space ex- 

 tending from it to the margin ; when decorticated however either 

 on the exterior or interior, the surface nacreous and shining. 

 Length nine-twelfths of an inch, diameter ten-twelfths. 



The above description from two specimens, found near 

 Peterhead, in January, 1843, and sent by Roderick Gray, Esq. 



Trochus crassus. Mont. Test. Brit. 281. Troclms crassus. 

 Flem. Brit. Anim. 323. 



GENUS 4. LITTORINA. P. 54, 135. 

 Littorina jugosa. Ridged Periwinkle. 



Shell subovato-conical, thick, with the spire a third 

 of the length of the last turn, which is tumid in the 

 middle, and marked with ten or twelve elevated, thin, 

 spiral ridges ; the aperture roundish, purplish-brown, 

 the outer lip thin. Jugdsus, ridged. 



Shell somewhat ovato-fusiform, thick ; with the spire from 

 a fourth to a third of the whole length, and tapering to a 

 small point; the whorls four, rather flat on the spire, with 

 the suture distinct ; the last turn very large, ventricose, with 

 ten or twelve prominent, sharpish, spiral ridges, and incon- 

 spicuous transverse striae, the colour dusky, yellow, or whitish ; 

 the aperture roundish, with the outer lip bevelled, and marked 

 externally by the spiral grooves, the inner reflexed, the inte- 

 rior purplish-brown. Length four twelfths of an inch, breadth 

 three and a-half twelfths. 



It differs from Littorina littorea in its form, and especially 

 its strong grooves and ridges ; but it is more allied to that 

 species than to Littorina rudis, and differs, I think, from 

 both species, its characters being in fact more prominent than 

 those of most species of its genus. 



On the rocky coasts, near low-water mark ; and in shell 

 sand on the beaches; not uncommon. 



Turbo jugosus. Mont. Test. Brit. 586. PI. 20. f. 2. Turbo 

 jugosus. Turt. Diet. 



GENUS 6. TUEBONILLA. 



Shell turrite, with the spire very elongated, tapering 

 to a fine point ; the aperture subovate, entire, with the 

 peristome incomplete behind, the outer lip thin, the 

 inner nearly straight, reflexed, leaving a small umbilicus. 

 Turbonilla, diminutive of Turbo* Eisso. 



