296 MAZATLAN UNIVALVES 
Famity CAPULID. 
Genus HIPPONYX, Defr. 
Cochlolepas, Klein. 1753:—H. & A. Ad. Gen. vol. i. p. 373. 
(Non Concholepas, Lam.) 
346. HIiproNnyx SERRATUS, 7. s. 
HI. t. conicd seu depressd, alba ; apice decollato, subcentrali 
seu valde remoto, interdum valde prominente ; lamellis crebris, 
acutis, extantibus, bast parallelibus, concentricé ornatd ; apicem 
versus radiatim costatd; supra lamellas radiatim tenuissime 
suleata ; basi latissimd, planatd, lamellis creberrimis instructd ; 
lamellis profundé serratis, lobis subquadratis ; inter lamellas 
epidermide fusca copiosissimé indutd, teniis incisis confertd ; 
cicatrice musculari transversim corrugatd. 
Proc. Zool. Soc. 1856, p. 3, no. 2. 
?= Hipponyx foliaceus, Mike. in Zeit. f. Mal. 1851, p. 36, 
no. 129, non Quoy & Gaim. 
This well marked species differs from H. antiquata, Linn. 
in the character of the base, which is broad and flat, made up 
of very numerous, close-set lamelle, deeply serrated into large 
searcely rounded lobes. The interstices are filled with epider- 
mis, in irregular ribband-like shreds as in Byssoarca Pacifica. 
The exterior, which rarely displays its characters satisfactorily, 
has slight tubercular ribs near the apex, which are continued 
over the lamelle as very fine, rather distant, indented strie. 
The apex is sometimes flat, sometimes high and curved back 
as in Emarginula rosea. It is always decollated and eroded. 
One extremely young specimen has the minute helicoid apex 
adhering to the spreading, rounded shell. The shelly base is 
almost always very thin and smooth, sometimes searcely per- 
ceptible. It is nearly related to an Australian species, probably 
H. foliaceus, Quoy ; but in that species the lamelle are serrated 
outside with the strong radiating sulci; the lobes of the basal 
lamine are more rounded; and the epidermis is finer and 
lighter. The largest specimen measures (from the very pro- 
jecting apex) long. 96, lat. °94, alt. °46. 
A very flat sp. 5 BG,” bis, inCreate 
A very conical sp. ge! GBs Yb a: tae AB. 
Hab.—Mazatlan ; gregarious, attached to each other, or on 
_ shells, (Byssoarce, &e.) rare; L’pool Col. 
