102 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



of sub-genera. It is for this reason that we admit Sinodia as a section 

 distinct i'rom Cordiopsis, of which it is the modern degenerate 

 representative." 



On the contrary, I am still of o])inion tliat botli Sinodia and 

 Cordiopsis belong to the genus Dositiia, and are altogetlier distinct 

 from Meretrix, though they are related to Pitaria. At the same time 

 I admit that there are some differences between the two gi'oups, and 

 I am quite willing to accept IT. Cossmaun's separation of them ; the 

 more so as he is able to associate several Miocene and Pliocene species 

 with C. incrussata. These are Cyprina gigas (Lam.), C. islandi- 

 coides (Lam.), Cordiopsis intercalaris (Cossmann), and Venus Brocckii 

 (Desh.) of the Italian Pliocene. M. Cossmann has figured the 

 three French Miocene species in the memoir referred to, and they are 

 evidently of the C. incrassata tj'pe. If, however, M. Cossmann means 

 that he would place Sinodia as a section of Cordiopsis he runs 

 contrary to accepted rules of nomenclature, for the name Sinodia 

 has priority. Cordiopsis must be regarded either as a section of 

 Sinodia or as a separate sub-genus of Dosinia. 



Summary. — Hitherto I have dealt chiefly with the descriptions of 

 sections and sub-genera given by other authors, and it will now be 

 desirable to mention the characters which I regard as the most useful 

 in distinguishing the subdivisions of Bosinia from one another, after- 

 wards giving brief definitions of these subdivisions. The characters 

 on which I rely are (1) the features of the lunule and escutcheon, 

 (2) the teeth of the left valve, (3) the presence or absence of a 4th 

 cardinal in the right valve, (4) the shape and depth of the pallial 

 sinus, (5) the presence or absence of a groove on tlie posterior margin 

 of the right valve, which receives a ridge on the rim of the left valve. 

 These characters are more or less correlated with one another, and by 

 them all the groups which have been mentioned may be defined in 

 a satisfactory manner. 



Bosinia (sensu stricto). — Lunule deeply impressed. Escutcheon 

 narrow, more or less excavated, but often ill-defined. In the L.V. 

 the anterior lateral is large and thick, middle cardinal broadly bifid, 

 the front part being united at top to the anterior cardinal. In the 

 R.V. there is a distinct 4th cardinal (long and narrow), and the 

 posterior margin has a narrow and shallow groove. Pallial sinus 

 long, narrow, obtuse or bluntly angular, and ascending. 



Bosinella (Dall). — Lunule shallow and lanceolate. Escutcheon 

 nari'ow and slightly excavated, but not well defined. In the L.V. 

 the anterior lateral is small or obsolete, the middle cardinal broad and 

 bifid, the front part being united at the top to the anterior cardinal. 

 In the R.V. the 4th cardinal is absent or very weak, and there is no 

 groove on the margin of the valve. The pallial sinus is deep, 

 ascending, of nearly equal width throughout and rounded at the end. 



Austrodosinia (Dall). — In this section the lunule is deeply impressed, 

 but the escutcheon is narrow and ill-defined, though often bordered 

 by ridges and sometimes excavated in the left valve. In the L.V. 

 the anterior lateral is strong and rugose, the middle cardinal thick 

 and solid, centrally placed between the other two. In the R.V. there 



