134 MALACOZOA. GASTEROPODA. PECTINIBRANCHlAfA. 



Several specimens found on fisliing-lines at Aberdeen and 

 the Cove. The first observed by Mr. Leslie, others by Mr. 

 Davidson, one by Miss Marion Macgillivray, in the Winter of 

 1841-2. In August, 1842, I found it also in fishing-boats at 

 Boddam, near Peterhead ; in September, it was found at Cru- 

 den by ]\Ir. Alexander Murray ; and, in December, by Mr. 

 Clark, at Banff. 



Trochus tumidus. Mont. Test. Brit. 280. PI. 10. f. 4.— Trochus 

 tumidus. Flem. Brit. Anim. 322. 



Genus 2. Phorcus. 



Shell roundish, rather depressed, tliickish, -with the 

 suture distinct, the turns convex, the aperture circular, 

 subangulate anteriorly, the peristome almost complete, 

 its columellar portion straightisli ; umbilicus deep. 

 Risso, Eur. Merid. iv. 133. 



1. PJwrctis Margarita. Pearly Phorcus. 



Shell roundish, rather depressed; with the mouth nearly 

 circular, the peristome rather thin, and discontinued only for 

 a small space ; the umbilicus deep and of moderate width ; 

 the last whorl very large, convex, the rest rapidly decreasing 

 to an obtuse tip ; the surface smooth, glossy, light brown, oli- 

 vaceous, or reddish, paler beneath, or whitish, the interior 

 nacreous and iridescent. Height two-twelfths, breadth three- 

 twelfths. 



Individuals vary much in colour. Frequently there is a 

 single reddish longitudinal band along the whorls. 



Common on Fuci ; as in the Bay of Nigg, at Slains, and 

 Banff. Frequent in shell sand on the beaches. 



Turbo margarita. Flem. Brit. Anim. 299. — Helix margarita. 

 Laskey, Wern. Mem. i. 408. PI. 8. f. 5. 



Genus 3. Skenea. 



Animal elongated, spiral ; with two filiform contrac- 

 tile tentacula, and round horny operculum. 



Shell orbicular, depressed, discoid; the whorls rounded; 

 the aperture circular, with the peristome complete. 



1. Skenea depressa. Brown Skenea. 



Shell orbicular, depressed, horny, transparent, glossy, almost 

 flat above, widely umbilicate beneath ; with four transversely 



