482 CRYPTOPLACINiE. 



Genus CRYPTOCONCHUS, Blainville. 



Mantle with a single series of pores, thick, smooth, 

 elevated at the pores into conical tubercles. 



Shell with the valves sub-cordate, with the exposed 

 part very small, linear, much longer than broad. 



Ex. C. porosus, Blainville, pi. 55, fig. 4. 



In this genus the valves are immersed in, and covered 

 by, the mantle, except" in the middle line ; the plates of 

 insertion of all the valves have only a single notch on 

 each side, which is sometimes rudimentary, and the 

 mantle-mai'gin is not beset with calcareous tufts of spicula 

 as in AcantliocJiites. A single species only is known, from 

 New Zealand. 



Genus ACANTHOCinTES, Risso, 



Mantle densely spinulose, surrounded with a series 

 of setigerous pores. 



Shell with the valves deeply immersed, sub-equal, ex- 

 ternally contiguous, with the exposed part moderate, 

 cordate, as broad as long. 



8yn. Acanthochitona, Gray. Acanthochitus, Phil. 

 Phakellopleura, Guild. Acauthochiton, Herrm. 



Ex. A. fascicularis, Linnaus, pi. 55, fig. 5. 



In this genus the plate of insertion of the anterior 

 valves is six-lobed, that of the middle bi-lobed, and that 

 of the posterior five-lobed. The species are from New 

 Zealand, the Canary Islands, the Indian Ocean, the 

 Mediterranean, arid the British Islands ; the margins of 

 insertion do not materially differ from those of Crypto- 

 conchus. 



