JDKES-BROWNE : SYNOPSIS OF THE VENEKID^. 91 



Amygdala has a wider range, extending from the west coast of 

 Europe through the Mediterranean and the Indian Ocean to the 

 Philippines, Australia, and New Zealand. Callithaca is the only 

 American representative. 



The tj'pical section of Paratapes, again, is Indo-Pacific, the type 

 being quoted from Natal, India, Tasmania, but Polititapes is 

 restricted to the Mediterranean and the western coasts of the 

 Old World. 



It has been supposed that the name Amygdala could not be used 

 for a mollusc because it was preoccupied for an Echinoderm. This 

 idea was based on a statement of Agassiz, who referred to '■'' Amygdala, 

 Van Phelsum, 1774", but ilr. Sherborn found that this was a mistake, 

 and that the name did not occur in Van Phelsum's work on Echino- 

 derms (see Index Animalium, p. 46). Neither can the name be 

 rejected on account of the Amygdalum of Megerle (1811) ; con- 

 sequently it can be accepted from Komer (1857), and since his first 

 species was Tapes decussatus, and this has been given in textbooks as 

 the typical example of Amygdala, that species should be regarded 

 as the type. 



The several groups above-mentioned are distributed in the three 

 genera Tapes, Paratapes, and Venerupis as follows. 



Genus Tafes, Megerle, 1811. 



Shell oblong, inequilateral, and generally expanded posteriorly ; 

 concentrically striated or radiately ribbed. Lunule defined, but 

 escutcheon often obscure. Ligament long and prominent. Hinge 

 with three divergent teeth in each valve, only three of the six being 

 bifid ; the left posterior directed backward so as to be nearlj' parallel 

 to the nymph. Valve-margins smooth. Pallial sinus fairly deep, 

 horizontal, and rounded. 



Tapes, s.s. Type, Venus litterata, Linn. 



Shell rather compressed, with small flattish umbones, concentrically 

 striated or grooved. Escutcheon defined, but narrow. Left median 

 tooth broad, triangular, and deeply bifid. Pedal scar separate from 

 adductor. 



Besides the varieties of 2'. lifteratus this group includes T. turgida. 

 Lam., 2\ sulcaria. Lam., T. desJiayesi, Hanley, 2\ similis, Desh., and 

 T. phenax, Pilsbry. 



Suh-getiera. 



Amygdala, Kiimer, 1857. Synonym : Ruditapes, Chiamenti, 1900. 



Shell convex, bearing radiate ribs which are more or less decussated 

 by concentric ridges. Escutcheon not defined. Hinge-plate narrow 

 and curtailed behind, so that the posterior teeth are both very short. 

 Pallial sinus deep. Pedal scar small and narrowly confluent with 

 that of the adductor. 



This group includes Tapes indiciis, Sow., T. rariegatus, Sow., 

 T. philippinani.m, Ad. & live., T. hruguieri, Hanlev, and T. intermedia, 

 Q. & G. 



VOL. XI.— JUNE. 1914. 7 



