276 DR. P. P. CARPENTER ON NEW SPECIES [Mar. 14, 
distantibus, crebre decussatis, jugo acuto; ar. lat. costis ii., 
validissimis, angustis, tuberculis angustis : intus marginibus 
suturalibus posticis planatis, haud tuberculosis, haud sinuatis; 
lam. insert. ut antea, sinu angusto, ad jugum 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. vil. validissimis: intus 
lumina cire. vil.-fissa, subygrunda planata. 
With a strong general resemblance to I. e/enensis, 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. 
Exvtus areis centr. lineis interdum parallelis, interdum radian- 
tibus, rugose scrobiculatis ; ar. lat. costis ii., validissimis, im- 
bricato-nodosis: valva antica costis similibus cire. ix.: v. 
post. area centrali lata; mucrone subpostico, planato; parte 
postica costis vil. similibus, medianis curtissimis, excurvatis : 
pallio squamulis minutis imbricatis. Intus v. ant. subgrunda 
(ut in Ischnochitone) munita, sed a costis pectinata ; dentibus 
acutis, intus linea undulata secundum costas instructa, extus 
concavis, parte convexa costarum incisis: v. medianis similiter 
pectinatis, laminis secundum costas diag. uniscissis : laminis 
suturalibus medio continuis, late sinuatis; suturis posticis a 
sculptura externa granulatis: v. post. viil.-lobata, marginibus 
planatis, laminis dense compressis incrassatis ; dentibus obtu- 
sissimis, appressis, haud extantibus, subobsoletis, extrorsum 
planatis, ut in v. ant. fissis; 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. 
Acma (? FLocCATA, var.) FILOSA. 
A. t. “A, mesoleucee”’ ‘forma et indole simili; sed sculptura multo 
