372 PROCEEDINGS OF THE NATIONAL MUSEUM vol. »s 



dent at a connects this subspecies with C. testudinaria . although in 

 other respects the structure of the compartments has not changed. 

 Whether typical C. patula occurs on the west coast of North America 

 or whether this species is represented by subspecies dent at a is an in- 

 teresting question, which cannot be answered until extensive collect- 

 ing has been done in this region. 



Genus CHTHAMALUS Kanzani 



CHTHAMALUS ANISOPOMA Pilsbry 



Plate 31, Figures 1-3 



Vhthamaii's anisopoma Pilsbury, 1916; Steinbeck and Ricketts, 1941. 



Localities: Cape San Lucas. March 19-40, on Acmaea atrata Car- 

 penter; Gabriel Bay, Espiritu Santo Island, April 12, 1940, on Ostrea 

 mexicana Sowerby ; San Francisquito Bay, March 31, 1940, on Acmaea 

 dalliana Pilsbry, with Tetraclita squamosa stalactifera f. confinis 

 Pilsbry; Port San Carlos, Sonora, April 4, 1940, on Tegula rugosa 

 Adams. 



Specimens of C. anisopoma from the above localities vary some- 

 what from those described by Pilsbry and from the general descrip- 

 tion given by Steinbeck and Ricketts. The parietes may be white or 

 buff, smooth (pi. 31, fig. 1), ribbed at base or strongly ribbed (fig. 2) 

 as in the type form. The specimens var}' in shape from come to 

 cylindrico-conic or they may be extremely flattened (fig. 3). The 

 largest specimen is 7 mm. in diameter and 3.5 mm. in height. 



Young barnacles have smooth parietes, which are usually dark 

 gray. In a specimen 1.5 mm. in diameter the orifice is closed by both 

 pairs of valves, and the right and left scuta and right and left terga 

 are similar in shape and size. They resemble the left valves of the 

 adult. Therefore this species is probably more closely related to C. 

 panamensis than to C. fissus. When the barnacle reaches the diam- 

 eter of 3 nun. the valves show the disparity in size and shape between 

 the right and left valves typical of the adult. 



