32 



NOTE ON THE BRITISH SPECIES OF ANOMIA. 

 By E. WiNCKwoRTH, M.A. 



Read 9th November, 1921. 

 (PLATE I.) 



The object of the present note is to emphasize the distinctions 

 between the four British species of Anomiidse. There is nothing new 

 in this ; Forbes and Hanley recognize four species, though 

 squamula is placed with epfnppium instead of with aculeata ; abroad, 

 Dautzenburg and Jensen among others distinguish them con- 

 chologically. Ridewocd in Phil. Trans., vol. 195, 1903, describes 

 the gill of A. aculeata and places this species with Dimya in a separate 

 suborder Dimyacea (I.e., p. 185) : he also figures A. ephijopium and 

 A. laqueata, the latter similar to patelliformis. 



I have recently examined numerous examples of this group from 

 Plymouth Marine Biological Association and elsewhere. All the 

 species are very variable in shape, thickness, and sculpture : and the 

 young of all four are discouragingly similar in appearance, while 

 the muscular scars are often very faint in small examples ; so that the 

 soft parts and above all the gill are a valuable aid to identification. 

 There is no need to section the gill or even to use a microscope ; a 

 good lens will at once show sufficient to determine the species, as 

 summarized below. 



ANOMIACEA. Anomiid^. 



Grenus ANOMIA, L., 1758. Type, A. ephippium, L. 



1. EPHIPPIUM, L., 1758. Upper or left valve with three distinct 

 muscular scars (PL I, f. 8). Grill W-shaped in section, and at once 

 recognizable by a dependent membranous flap of the outer ascending 

 lamella, the fifth lamella of Lacaze Duthiers (PJ. I, f. 1). 



Genus MONIA, Gray, 1849. Type, A. zelandica, Gray, in DiefEenbach, 



1843. 

 I do not like referring British species to a New Zealand genus, 

 but as I have only seen the shell of zelandica, and can see no con- 

 chological reason for not including our species under the same genus, 

 I must at present leave the two following species here. 



2. PATELLIFORMIS, L., 1761. The original description in Fauna 

 Svecica is not quite satisfactory, and suggests the next species, but 

 the figure given in N. Act. Upsala 1773 confirms the usually accepted 

 identification, and in each case the species is mentioned as received 

 from A. R. Martin. Hanley states that the types in the Linnean 

 cabinet were introduced by the younger Linne. 



Upper valve with two muscular scars, which are separate and 

 distinct (PI. I, f. 9). The typical sculpture may be almost obsolete, 

 and, indeed, is quite absent in very young examples, or may be 



