36 \ \\TIIOCHITE8-CRYPTOCONCIirs. 



Valves entirely covered by the girdle except a ////"// arta "t the 

 ,-i'l'/' nfmrli. /'.- '/ having the in$ertion-plaie with several 



i slits, anterior valve .Vslit. Girdle leathery, naked, bearing a 

 series (18) of sutural tufts on tubercles, or pores, sometimes sub- 

 obsolete, along the sides of the valves. Gills extending along the 

 posterior half of the foot. 



Tliis subgenus cannot in fairness be dated from the time of its 

 pnllication in Burrow's El ;<>r in that work it is in no way 



defined and i< disowned as a valid genus. Burrows simply says that 

 Hlainville has affixed the names Oryptoeonchiuporosustaid C.larvce- 

 formis to two specimens in the British Museum. The latter belongs 

 of course to ChitonMw. In 1829, GoUding adopts Cryptocont-hn." 

 as a genus, and gives a generic diagnosis. Blainville himself ignores 

 tin- name in his publication on Chitons in 1825, believing it a 

 -ynonym of <'hitii' /hu. 



This irroup is much more closely allied to Acanthochitf* than to 

 . its valves being exactly the form which would be pro- 

 1 by a little further covering of the side areas in a species like 

 .4. (yotoplar) h< inp/nlli. The backward prolongation of the sides 

 into posterior lobes is just as great in that species; the main differ- 

 ence being that in yfi,j f /nx these posterior lobes are not covered by 

 _inlle. The structure of the tail valve is practically the same in 

 / \boplax and Cryptoconchm. 



A. POROSUS Burrow. PL 3, figs. 57, 58, 59, 60, 61, 62. 



Shell elongated, all but a linear dorsal area of each valve covered 

 by the integument continued upward from the girdle, but in the 

 dri -d -tatf showing through it the posterior outlines of the valves. 

 Color when dry dark reddish or blackish-brown. 



' outer layer of each intermediate valve is reduced to a narron- 

 dorsal area, shu/i'd lib >. <>/, ,,,i<t (inn jn,int icithont the dot (') ; 

 upon each sideof i . ///* posterior ?/<<//</''" f fn-h r.tlr, is pro- 



'i baclnvard in a round' d 1<>I><' } showing plainly through the con- 

 tracted out<r skin. A more or less developed groove extends to the 

 lateral slits. Head and tail valves with minute circular exposed 

 dots. 



Interior light blue-green. Anterior valve having 5, median 

 < 1, posterior 5-7 slit^. 



: ddisli- or blAckiab-brOWH in the dried condition, nuked, 

 smooth, l"ith> rn : / ,/ tubercles each n-ith <i 



