AND VARIETIKS OF CHITONID^ AND ACM.EID^. 2/6 



distantihus, crehre decussatis, jiiyo acuto ; ar. lat. costis\\., 

 vnlidissiiuis, aiiyustis, tuberculis avyustis : intus marginibus 

 suturahbiis jiosticis plaiiatis, haud tubei'culosis, hand sinuatis; 

 lam. insert, ut anted, soiu angusto, ad juyuin ariyulato. Vulra 

 antica costis x., vnlidis, angustis: intus ut antea, sed fssuris 

 viii. Valca j)ostica mucrone postico, planafo ; parte postica 

 eocpansa, huud concava, costis circ. vii. validissimis : intus 

 lamina circ. \'\\.-Jissa, subyrunda plunata. 

 With a strong general resemblance to I. elenensis, the diflFerences 

 in detail in the only two specimens examined, as above stated, ap- 

 pear of specific importance. If only varietal, it is equally important 

 to notice how much change is tolerated by the habits of the animal. 

 It may be the shell called Chiton clathratus by Prof. Adams, of which 

 there were no duplicates to compare. It offers a still more marked 

 transition to Callochiton, the margin of the posterior valve being 

 somewhat pectinated by the great projection of the ribs. 



"Callochiton" pulchellus: diagn. auct. 



Extus areis centr. lincis interdum parallelis, interdum radian' 



tibus, ruyose scrobiculatis ; ar. lat. costis ii., validissimis, im- 



bricato-nodosis : valva antica costis similibus circ. ix. ; v. 



post, area centrali lata; mucrone subpostico, planato ; parte 



postica costis vii. similibus, medianis cvrtissimis, excurvatis : 



pallio squamulis miniitis imbricatis. Intus v. ant. subyrunda 



(ut in IschnocliitoneJ munita, sed a costis pectinuta ; dentibus 



acutis, intus linea unduluta secundum costas instructa, extus 



concavis, parte convexu costarum incisis : v. medianis similiter 



pectinatis, laminis secundum costas diay. uniscissis : laminis 



suturalibus medio continuis, late sinuatis; suturis jjosticis a 



sculptura externa yranulatis : v. post. y'li. -lobata, maryinibus 



planatis, laminis dense compressis incrassatis ; dentibus obtu- 



sissimis, appressis, haud extantibus, subobsoletis, extrorsum 



planatis, ut in v. ant. Jissis ; interdum Jissuris quuque in pur- 



tibiis concavis. 



As I have seen no published diagnosis of the very peculiar type of 



insertion-plates observed in this species, which has hitherto been too 



rare to allow working naturalists an opportunity of dissection, I have 



given a minute description. The plates of insertion, as well as the 



exterior eaves, are scalloped by the strong ribs, and alternate with 



them. In the posterior valve the eaves are flattened outwards, in 



closely appressed layers, the blunt, ill-developed insertion-teeth 



lying flat upon them. The valves easily separate from the mantle, 



when immersed in water. Outside, the species is easily recognized 



by the two strong ribs of the diagonal areas, the central pitted iu 



somewhat branching rows, and the ribs on the curiously flattened 



posterior valve resembling a clenched fist. 



AcMiEA (? floccata, var.) filosa, 



A. t. "A. mesoleuc3e"y(y/vrta et indole shnili ; sed scidptura midto 



267 



