196 



BULLETIN 93, UNITED STATES NATIONAL MUSEUM. 



the posterior ramus over three-fourths the length of the anterior. 

 Cirrus ii has slightly unequal rami of 9 segments. Posterior cirri 

 with three pairs of spines on the segments. By the proportions of the 

 rami of the first cirrus, this form differs strongly from B. h. nip- 

 ponensis (station 5003), but otherwise is much like it. 



Several other lots are labeled Alaska, without nearer indication of 

 localit}^ 



BALANUS HESPERIUS form L.ffiVIDOMUS, new form. 

 Plate 50, fig.s. 1-1/; 2-2&. 



Type.— Cat No. 2106, Acad. Nat. Sci. Phila., from San Juan 

 Islands, Puget Sound, collected by Homer AVheeler. 



Distribution. — Monterey, California, to Alaska. 



The shape varies from broadly conic to shortly cylindric. The 

 external walls are smooth in the typical form of the subspecies ; the 

 ribs on the inner faces of the parietes are regular. The scutum has 

 fewer, more widely spaced groAvth-ridges than in hesperius; they are 

 often low, or very weak. The basal margin of the scutum is usually 

 longer. 



I segregate this form with some hesitation, yet after going over 

 the material repeatedly there seems to be a constant difference in the 

 external sculpture of the scuta, which it Avould be a fault to ignore. 



As the geographic ranges of the two forms overlap in the north 

 and there are some transitional specimens, I do not call it a sub- 

 species. 



