278 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



have a rather thick shell, like Solidula, to which they seem more properly to 

 belong. 



The genus Actceon, as here understood, seems to date back to the 

 Triassic epoch, and ranges through all the succeeding rocks into our existing 

 seas. It is probably not more numerously represented, however, at present 

 than during the Cretaceous and Tertiary periods. The recent species are 

 found in tropical and some more northern seas. One occurs in the Mediter- 

 ranean and British seas, and a very similar species is found on the north- 

 eastern coast of the United States. About sixteen to eighteen recent species 

 are enumeratedin conchological works, though this enumeration, of course, dees 

 not include nearly all of the existing species. 



Note. — Perhaps this may be the most appropriate place tor me to notice 

 some criticisms in which Dr. Stoliczka has indulged, in the second volume 

 of his Palaeontologia Indica, (if a paper (if mine published in the American 

 Journal of Science and Arts, in I860, on the family Actmonidce. His stric- 

 tures are written in his usual supercilious style, and hardly require any other 

 reply than the simple statement (if the fact that (as a result of all his objec- 

 tions) of the ten old groups included, and the three new ones proposed by me, 

 as good and distinct genera of this fondly, as well as a new subfamily at the 

 same time proposed, he admits nine of the old genera, with the new sub- 

 family, and only rejects one of the new genera. The old genus not included 

 by him is Globiconcha, d'Orbigny, which is generally referred to this family, 

 though it was founded (in imperfect and unsatisfactory materials. 



The newly-proposed genus Aptycha that he rejects, was intended for the 

 reception of an East Indian Cretaceous shell, described many years back by 

 Prof. E. Forbes. It has the form, thickened outer lip. and general appear- 

 ance of Ringicula, but was clearly figured and distinctly described by Professor 

 Forbes as having its inner lip destitute of any traces of folds or plait*; 

 a combination of characters which any well-informed conchologist of the 

 present day, will at once see would mark it as the type of a new genus, as 

 the genera of this family are now more precisely restricted. Dr. Stoliczka, 

 however, states that, on examining Professor Forbes's original type-specimen 

 (which, of course I never saw), in London, he found, after clearing the rock 

 out of the aperture, that it really has the plaits of Ringicula on its inner lip. 

 This being the case, my name Aptycha necessarily falls into the synonymy 

 of that gfenus ; but I think any fair-minded naturalist will admit that the 



