AND VARIETIES OF CHITONIDJC AND ACM.EIDJE. 276 



distantibus, crebre decussatis, jugo acuto ; ar. lat. costis ii., 

 validissimis, angustis, tuberculis angustis : intus marginibus 

 suturalibus posticis planatis, hand tuberculosis, haud sinuatis; 

 lam. insert, ut antea, sinu angusto, adjugum angulato. Valva 

 antica costis x., validis, angustis: intus ut antea, sed fissuris 

 viii. Valva postica mucrone postico, planato ; parte postica 

 expansa, haud concava, costis circ. vii. validissimis : intus 

 lamina circ. \\\.-Jissa, subgrunda planata. 



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

 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, rugose scrobiculatis ; ar. lat. costis ii., validissimis, im- 

 bricato-nodons : valva antica costis similibus circ. ix. : v. 

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

 postica costis vii. similibus, medianis curtissimis, excurvatis : 

 pallio squamulis minutis imbricatis. Intus v. ant. subgrunda 

 (ut in Ischnochitonej munita, sed a costis pectinata ; dentibus 

 acutis, intus linea undulata secundum costas instructa, extus 

 concavis, parte convexu costarum incisis : v. medianis similiter 

 pectinatis, laminis secundum costas diag. uniscissis : laminis 

 suturalibus media continuis, late sinuatis; suturis posticis a 

 sculplura externa granulatis : v. post, \ii.-lobata, marginibus 

 planatis, laminis dense compressis incrassatis ; dentibus obtu- 

 sissimis, appressis, haud extantibus, subobsoletis, extrorsum 

 planatiSy ut in v. ant. Jlssis ; interdum fissuris quoque in par- 

 tibus 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 in 

 somewhat branching rows, and the ribs on the curiously flattened 

 posterior valve resembling a clenched fist. 



(? FLOCCATA, var.) FILOSA. 



A. t. "A. rnesoleuc8e"/ orwza et indolesimili; sed sculptura multo 



267 



