148 Mr. W. Nicoll on Trematode 



XVIII. — Sote on Bulimulus (DryniJtus) citrinellus, /y/'.,an(7 

 scitulus, Reeve. By Hugh C. Fulton. 



B, ciTSiNELLVS was fiist published b}'' Pfeiffer in liis Monog. 

 Helic, Viv. vol. vi. p. 114 (1868), as a " var. P^*' of B. scitulus, 

 Rve., with the following description : — " Anfractibus paulo 

 convexiovibns, strigis spadiceis nullis.^' The latter |)art of 

 this is transsluted in Tryon's 'Manual,' vol. xi. p. 271, as 

 liaving " no scarlet streaks " ; this should have been " no 

 brown streaks/' As a matter of fact, specimens which I 

 believe are properly referred to PfeifFer's citrinellus have very 

 pale orange or scarlet stripes, but no brown ones as seen in 

 scitulus. 



I have before me a large number of both scitulus and citri- 

 nellus coWecitdi in 18*J4 by Mr. Baron, the former at Cajamarca, 

 Peru, and the latter at Cajabamba, Peru. Among the 

 specimens of citrinellus are some answering to PfeitFer's 

 description, whilst others are ornamented with orange and 

 dark brown streaks, so that Pfeifler's description does not 

 suffice for the material now under consideration. Citrinellus 

 is easily separated from scitulus; the latter in the adult state 

 is a smaller shell, with much narrower and more numerous 

 streaks, generally narrower in form, with its peristome more 

 contracted at its anterior or basal area, and its whorls increase 

 more rapidly than in scitulus, consequently the body-whorl is 

 obviously larger. 



Pfeiffei's description of the whorls of citrinellus as " paulo 

 convexioribus " is scarcely borne out by the majority of the 

 specimens before me ; if there is any difference worth men- 

 tioning, 1 sliould say the body-whorl of scitulus is the more 

 convex of the two, but the specimens vary in this respect. 



The darker form of B. citrinellus is well illustrated in 

 Tryon's ' Manual,' vol. xi. pi. xlvii. fig. 17; the figure 16 on 

 the same plate is a not very faithful copy of the excellent 

 figure of Reeve's scitulus as given in the (Jonch. Icon, 

 pi. xcvii. fig. 513. 



XIX. — Notes on Trematode Parasites of the Cockle 

 (Cardium edule) and Mussel (Mytilus edulis). By 

 \ViLLiAM Nicoll, j\I.A., B.Sc, Gatty Marine Laboratory, 

 St. Andrews. 



[Plate IV.] 



In April 1903, at the suggestion of Professor M'Intosh, I 

 commenced the examination of the edible coeklc (C. edule) 



