OF CONCHOLOGY. 241 



The preceding synonymy refers to the genus Acmcea, Esch- 

 scholtz, as a whole, the following to the subgenus as now restricted. 



Subgenus Acm^ea, [sensu stricto) Esch. Philippi., 1846. 



Cren. char. Animal unprovided with a branchial cordon of 

 lamellos'or any similar appendages between the mantle and the 

 foot. Radula provided with three, subequal, similar, simple 

 lateral teeth on each side, arranged in a line which forms 

 an angle with the rhachis, each tooth being laterally and trans- 

 versely parallel with the corresponding tooth in the opposite side, 

 and the longitudinal axes of all the cusps being nearly or quite 

 parallel with the median line of the radula which is destitute of 

 uncini. Muzzle frill produced at the lower anterior corners 

 into two lappets or tubercles. Shell solid, with an erect or an- 

 teriorly inclined apex. 



Type AcMiEA mitra, E.sch. 'Plate, 14, fig. 1. 



Syn. Acmcea mitra, (Esch.) Rathke. Zool. Atlas, part v. p. 

 18, No. 1, pi, xxiii, fig. 4. 



Acmoia mammillata, Esch., ib., p. 18, No. 2. 



Acm(^a marmorea Esch., ib., p. 19, No. 3. 



Scurria mitra, Grray, Adams, Cpr., &c., (pars.) 



Lottia conica, Gld., Moll. U. S. Expl. Exp. p. 346, (maxima 

 pars.) 



Scurria ? 7nitra, Dall, Am. J. Conch, v. p. 149, pi. xv, 18G9. 



Not Scurria mitra, Alcock (MSS.) Am. J. Conch, ii, p. 345 

 =^Scurria scurra Less., nor 



Scurria scurra, Lesson as aver Gray, Adams, D'Orbigny, 

 and others. 



Soft parts of a waxen white. Foot short, subcircular, smooth 

 below and on the sides. Thickened portion of the mantle edge 

 narrow, perfectly smooth all round, thinner portion ditto. Head 

 short, stout ; muzzle broad, transversely oval, furnished with a 

 narrow, granulose frill which extends entirely around it, and at 

 the lower corner on each side is produced into a sort of tuber- 

 cle. Between these tubercles, below, the frill is very narrow. 

 Disk of the muzzle granulose, radiately grooved. Mouth horse- 

 shoe shaped. Tentacles in the adult moderately long, cylindrical, 

 very little swollen at the base, which is constricted without any 

 tubercle on the inner side as in most of the Patellce ; tips bluntly 

 rounded. The very young have the tentacles more swollen and 

 pointed, proportionately. Eyes small, black, on the upper pos- 

 terior bases of the tentacles. Gill stout, attached to the mantle 

 a little to the left above the head ; pointing forward a little to 



