﻿I3O SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 47 



into two families, for the first of which it will be convenient to 

 retain the familiar name Rancllidcc, it now becomes a question as to 

 what we shall call the family containing- the Tritons, since the names 

 Triton and Tritoninm for these Mollnsks are no longer available. 

 Lotorium is a synonym of Cymatium and need not be discussed fur- 

 ther, so Lotoriidcc is out of the question. Lampusia was originally 

 equal to Septa + Cymatium pileare Linne, and if retained at all 

 must be as merely a subordinate section of that genus. Hence, ac- 

 cording to the rule governing such matters, it is not suitable as a ba- 

 sis for the family name. The shells forming the genus Septa have 

 always been regarded as the typical triton shell and have been so 

 denominated colloquially for two centuries. Though the number of 

 species is not large they attain as individuals a larger size than species 

 of any other group in the family, and indeed are among the largest 

 and most widely distributed gastropods. There seems therefore to be 

 no reason why the family name Septidce, which is shorter and more 

 euphonious than a name which might be formed from Cymatium, 

 should not be adopted as suggested by me in 1901. 



I have not found that Mr. Kesteven's groups, when tested by com- 

 paring the species, could be accepted without some transfers, as in- 

 deed he himself suggests may be necessary, but, in the main, they 

 are sufficiently natural. An absolutely final arrangement could be 

 attained only by making a critical study of the nomenclature and char- 

 acteristics of each of the known species, which would be a work of 

 years. The following grouping, utilizing the names on record, will, 

 however, serve as a step in advance of the present state of the sub- 

 ject. I preserve the geological order. 



Family SEPTID.E 

 Genus TRACHYTRITON Meek, 1864 

 Type T. vinculum Hall and Meek. Cretaceous. 



Genus PERSONELLA Conrad, 1865 



Type P. septemdentata Gabb. Eocene. Recent analogue Triton 

 quoyi Reeve. Synonyms: Sassia (apenninica) Bellardi, 1873; 

 Semiranella De Gregorio, 1880. 



It is impossible to say whether the very close similarity in nucleus, 

 >ize. and shell characters between the fossil types and T. quoyi, indi- 

 cate- the persistence of all the characters over such an enormous 

 period of time, but without some evidence to the contrary we are per- 

 haps justified in provisionally assuming it to be so. The Eocene 



