186 Misce llaneo us. 



and Clypidella, also Puncturella and Emarginida ; Dentaliadce by 

 two or more species ; Tecturidce by several species of Acmcma, also 

 by Scurra, Oadinia by one and Nacella by six or more species ; 

 Chitonidos by numerous species and great numbers of individuals. 



It may be tbat some of tbe groups included by the Messrs. Adams 

 in tbe order referred to, as our knowledge increases, will require to 

 be separated or removed; but so far as the purposes of comparison 

 as made herein are concerned, the result will not be materially 

 impaired. 



The total number of marine molluscan species and well-marked 

 varieties within the Californian and Oregonian province, so far as 

 known and determined, is not far from 630, of which about 200 are 

 Bivalves ; and of the remaining 430, 123 are included within the 

 Scutibranchs ; of this latter number about 40 belong to the Chitonidae, 

 and the same number to the Trochidse. 



Of the 247 marine gasteropods enumerated by the late Dr. Stimp- 

 son, in the Smithsonian-Institution Check-list, as found from the 

 arctic seas to Georgia, 32 only, or less than one eighth, come within 

 the order mentioned ; of this comparatively small number, seven are 

 Chitons and fourteen belong to the Trochidce, while Haliotis* is with- 

 out a representative : the Trochidce within this province are not 

 characterized by such marked or unique characters as distinguish their 

 relatives on the west coast. 



Some revision may be required hereafter in the number of Scuti- 

 branchiate species credited to the west-coast province, as forms now 

 catalogued as distinct may, in some instances, be united ; but, on the 

 other hand, it is not unlikely that new forms undoubtedly distinct 

 will be detected when the coast is more thoroughly explored. — Pro- 

 ceedings of the California Academy of Sciences, October 7, 1872. 



The Megalops Stage of Ocypoda. By S. I. Smith. 



The Monolepis inermis, long ago described by Sayf, and partially 

 figured by Dana J, is undoubtedly a stage in the development of Ooj- 

 p>oda arenaria. The large size and peculiar structure of this megalops 

 render it one of the most interesting forms of the group of larvae to 

 which it belongs. It is closely allied to the Monolepis orientalis, Dana, 

 from the Sooloo Sea, figured in detail on plate 31 of the Crustacea of 

 the "Wilkes's Exploring Expedition. The carapax is very convex 

 above and narrowed toward the front. The front is deflexed and 

 the extremity tricuspidate, the median tooth being long and narrowly 

 triangular, while the lateral teeth are small and obtuse. The sides 

 are high and impressed, so as to receive the three anterior pairs of 

 ambulatory legs. The third pair of ambulatory legs are closely ap- 

 pressed along the upper edge of the carapax, and extend forward 

 over the eyes, the dactyli being curved down over the eyes and along 

 each side of the front. The posterior legs are small and weak, and 



* A solitary specimen of Haliotis, of small size, was obtained through 

 dredging in the Gulf-stream, four or five years ago, b} r Count L. F. Pour- 

 tales, of the U. S. Coast Survev, but south of Georgia. 



t Journ. Acad. Nat. Sci. Philad. 1817, vol. i. p. 157. 



j Crustacea of Wilkes's Expl. Exped. pi. 31. fig. 6. 



