OF CONCHOLOQY. 337 



proaches the central portion. When about one-fourth of an 

 inch long, the shell is usually of an orange-yellow, with two 

 conspicuous brown rays, others also appearing; non-rayed 

 specimens are, however, common. In its early adolescence, 

 irregular decorticated shells are the A. monticola of Nutt., ms.; 

 some specimens not being distinguishable internally from Lottia 

 onychina, Gld. This, however, is rightly assigned to Kio Ja- 

 neiro, being identical with A. subrugosa, D'Orbigny, from 

 Brazil. 



Some of the specimens called A. strigillata, Nutt., ms., also 

 belong to this stage, being the variety in which the stripes are 

 tine and uniform. Others, however, are probably varieties of 

 A. patina. In the Rev. J. Rowell's collection, there is a very 

 remarkable exaggeration of this variety from Sta. Cruz, called 

 tesselata, Nutt., in Mus. Cuming, in which (after the horny 

 commencement) the shell developes three conspicuous olive- 

 brown stripes over the back, broadly bordered on each side 

 with white, the interstices with olive, scarcely dotted with 

 light. Near the margin, however, it rather suddenly devel- 

 opes the ordinary strigate pattern. The shell is smooth, and 

 must have lived on choice food in still water. The usual color 

 inside is china- white, often tinged with yellowish. The border 

 is normally with a very narrow dark rim, and dark scollops 

 between the ribs. These sometimes assume the form of faint 

 tesselations or dots, and, in rare instances, are nearly or quite 

 absent. In the middle is an irregular brown blotch, often 

 faintly developed, sometimes quite absent. Very rarely the 

 shell is deeply tinged with rich purple-brown, with broad, 

 colored margin, leaving only a narrow belt of white. There 

 is little doubt that the food alters the color of the animals, as 

 well as of the shells. 



Some specimens of the form textilis appear most naturally 

 to belong to this species, though they present, more or less, 

 the freckled painting of A. persona. The apex, moreover, is 

 rather more anterior than is usual in this species. They may 

 be hybrids. 



ACM^A PERSONA, Esch. 



Zool. Atlas, p. 20, pt. 5, pi. 24,/. 1, 2, -f A. radiata, Esch.= 

 A. ancylus, Esch.+^L. digitalis, Esch.: loc. cit. 



= A. Oregona, Nutt. Var.=A. scabra, Gld., pars, (f. 456, 

 456a, excl.) non Nutt. 



Var.—A. umbonata, Nutt. 



YiiT.=A. textilis, Gld. 



The following are the principal forms:— 1. Normal: strong- 

 ly developed, = A. Oregona, Auct. Shell large, arched, 

 with strong, rounded ribs and broad interspaces, coarsely 



