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A SYNOPSIS OF THE FAMILY VENEEID^. PAET II. 

 By A. J. Jukes-Bkowne, F.R.S., F.G.S. 



Read 13th March, 1914. 



I HAVE followed Gray and Deshayes in dividing the Veneridae into 

 sub-families, but into two only, the Meretricinie and tlie Venerinse, 

 according to the presence or absence of an anterior lateral tooth. By 

 this criterion the genus Antigona is separated from the genera Venus 

 and Chione, but I do not wish it to be supposed that I regard these 

 two sub-families as two distinct lines of evolution. On the contrary, 

 I think each series includes several stirpes or branches of development, 

 and I think that the Chione group has been developed directly from 

 the Antigona stock by suppression and elimination of the anterior 

 lateral tooth. 



On this point I again find myself in disagreement with Dr. Dall, 

 Avho imagines that there are important anatomical differences between 

 the animals of Chione and Antigona, and thinks that the possession of 

 an anterior lateral is correlated with such differences. In his own 

 words, "there is not a priori any very good reason wliy the presence 

 or absence of a minute pustule of shelly matter in front of the cardinal 

 teeth should count for much in the classification of species (or) genera, 

 or still less be the criterion for determination of the sub-family to 

 which a species belongs. Yet in making comparisons of tiie anatomical 

 features of these animals this little tooth or pustule is found an 

 excellent index to important anatomical difterences. So, whether 

 it has any intrinsic value or not its correlation with important 

 characters must be admitted." ^ 



Dr. Dall, however, does not state what these characters are or how 

 the animal of Antigona, wliich he calls Cytherea, differs from that 

 of Venus and Chione. He only states under the head of Meretricinaj 

 that tliey have "siphons of moderate length with papillose orifices, 

 the tubes united for a great part of their length, the margin of the 

 mantle largely free, more or less papillose, the foot large, hatchet- 

 shaped, not byssiferous " ; and that in the Venerinse "the siphons 

 are usually comparatively sliort and more or less separate from otie 

 another. The foot is hatchet-shaped, and in the adult not byssiferous 

 except among the nestlers ". He might also have added that the 

 mantle-margins are free and generally fringed, and that the orifices 

 of the siphons are often cirrliose ; and lie should have said that the 

 length of the siphons varies much in different genera. 



It will be seen, therefore, tluit in the characters which are generally 

 considered to be of importance for the purposes of comparison there 

 is no essential difference between the animals of the Meretricina) and 

 Venerinse, unless he intended to signify that the siphons of the latter 

 are always more separate than those of the former. On this point 



^ Trans. Wagner Free Inst. Science, vol. iii, pt. vi, p. 1281, 190.3. 

 VOL. XI. — JUNE, 1914. 6 



