134 MALACOZOA. GASTEROPODA. PECTINIBRANCHIATA. 



Several specimens found on fishing-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 Mr. Alexander Murray ; and, in December, by Mr. 

 Clark, at Banff. 



Trochus tumidus. Mont. Test. Brit. 280. PL 10. f. 4. Trochus 

 tumidus. Flem. Brit. Anim. 322. 



GENUS 2. PHORCUS. 



Shell roundish, rather depressed, thicldsh, with the 

 suture distinct, the turns convex, the aperture circular, 

 subangulate anteriorly, the peristome almost complete, 

 its columellar portion straightish ; umbilicus deep. 

 Risso, Eur. Merid. iv. 133. 



1. Phorcus 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 SJcenea. 



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

 flat above, widely umbilicate beneath ; with four transversely 



