JDKES-BROWNE : ON SOME GENERA OF VENERID^. 235 



nomenclature, reserving all explanations for his memoir on the 

 Tertiary Fauna of Florida, which was puhlished in the following 

 year.^ 



Eoth in his Synopsis and in the larger memoir Dr. Dall places 

 Gomphina as a subgenus of Ghione, in spite of many obvious diiferences. 

 The type is given as V. tmdulosa, Lam., without comment. On 

 p. 1289 of the later memoir he gives a brief diagnosis of Gomphina, 

 which, however, is much less accurate than that given by Homer. 

 The first sentence reads, " valves more or less extended behind and 

 pointed " ; he fails to notice the thick triangular tooth of the right 

 valve, but says " the posterior right and two anterior left cardinals 

 grooved." 



He proceeds to divide the group into two sections, namely — 

 Section Gomphina, Morch, s.s. Type, V. tmdtdosa, Lam. 

 ,, Macridiscus, Dall. ,, V. ceqxiilaUra, Sow.^ 



The first is defined as having reciprocal rugosities on the right 

 nymph and on the left posterior cardinal, and he then remarks : 

 " Tapes pinguis, Sowerby, is really more typical of this group than 

 the nominal type." 



Macridiscus is thus defined: "Nymphs and teeth smooth, entire; 

 valves in general more compressed, equilateral, and trigonal than in 

 the preceding section ; less heavy and sometimes with feeble striation 

 distally. V.faba, Eeeve, and V. fumigata. Sow., seem to belong to 

 thi* section. It is Gomphina, H. & A. Adams, not Morch." 



Several of these statements are very far from being correct. In 

 the first place, the first sentence about the shape of the valves is 

 not true either of V. nndtdosa or of V. ceqiiilaiera, though it would 

 apply to Tapes pinguis and its allies. T. pinguis, however, is so 

 different from Gomphina, whether that is typified by V. undulosa 

 or V. donacina, that no other conchologist has ever placed them in the 

 same subgenus. It was included by Eomer in his Hemitapes, and is 

 certainly more closely allied to that group than to Gomphina. Dr. Dall, 

 therefore, first assumed that certain species should be transferred from 

 Hemitapes to Gomphina, and then tells us that one of them is more 

 typical than the type ! 



Again, he asserts in his general description that three of the teeth 

 are grooved, while under '■Macridiscus^ he says its teeth are entire and 

 smooth. Both these statements are incorrect. In most specimens of 

 V. undulosa the only grooved tooth is the right posterior, all the teeth 

 in the left valve being entire, but there are occasional specimens in 

 which the median tooth of each valve is grooved. In V. donacina, 

 however (and its var. cequilatera), both the median teeth are distinctly 

 grooved. As regards smoothness, I have observed that in V. donacina 

 the left posterior cardinal always has one or two elongate grooves on 

 its upper side, though it is not so rugose as in V. undulosa. 



' Trans. Wagner Free Inst. Science, 1903, vol. iii, pt. vi. 



^ He does not explain why he gives fpqiiilalrra as his type instead of do»ncina. but 



probably he considered them as identical, and will not acknowledge Chemnitz as 



a Ijiuomial author. 



