ACM.EA. 11 



loidea alveus COUTH., Best. Journ. N. H, ii, p. 177. Lottia alveus 

 GLD., Inv. of Mass., p. 154, f. 13. lectura alveus BINNEY in 

 GOULD, Inv. of Mass., 2d edit., p. 269, f. 530. Acmcea testudinalis 

 var. alveus DALL, Proc. U. S. Nat. Mus. 1878, p. 340. 



Atlantic specimens of this well-known shell, although very vari- 

 able in size and coloration, are readily distinguished from the other 

 forms, the only considerable divergence being found in var. alveus. 

 Specimens from the Aleutian Is., according to Dr. Dall, completely 

 bridge the gap between testudinalis and patina. I have retained 

 the latter separate, simply as a matter of convenience ; but I do not 

 doubt that it must be regarded as a geographic race of testudinalis. 



American specimens are generally larger than European ; figs. 

 27-29 represent specimens from Maine, figs. 25, 26 from England. 



Var. ALVEUS Conrad. PI. 42, figs. 90, 91. 



Small, thin, compressed at the sides; apex acute and a little 

 hooked forward. Surface delicately striated, interruptedly striped 

 or tessellated with brown. Inside showing the markings of the 

 exterior. 



Massachusetts to Arctic Ocean ; Sitka northward. 



Numerous transitions occur between this and typical testudinalis. 

 The narrow form is caused by the residence of individuals on sea- 

 weed or Zostera fronds. 



** * 

 II. SPECIES OF THE WESTERN COAST OF NORTH AMERICA. 



The author has examined specimens of all of the species of this 

 region, including many original types. Of most species many 

 hundreds of shells have been studied. The elaborate papers of 

 Dr. P. P. Carpenter, and of Dr. Win. H. Dall have been freely 

 used. 



A. PATINA Eschscholtz. PL 2, figs. 34, 35, 36, 37 ; pi. 9. figs. 6-14. 



Shell large, oval or rounded-oval, depressed-conic, the apex 

 rounded and near the middle; slopes slightly convex. Surface 

 obsoletely radiately striated, olive-gray, tessellated, or more rarely 

 striped, with black. 



Inside white with an irregular brown central area and a rather 

 wide dark or tessellated border. Length 53, breadth 46, alt. 18 mill. 



Aleutian Is. to San Diego, California. 



