596 RITTER. 



1 8, it hardly seems possible that Stimpson could have erred so 

 widely as this. His statement that the " filaments at the summit 

 of the branchial sac of C. coriacea appear to be few, and shaped 

 like the palpi of the bi-valve acephala " I am at a loss to know 

 how to interpret, but it certainly seems that if he had been 

 examining our species the large branchial tentacles could not 

 have escaped his notice, and certainly had he seen them he 

 could not have compared them to the palpi of bivalve molluscs. 

 On the whole I am inclined to think that his C. coriacea is in 

 reality a Stycla. 



The nearest allies of these two closely related species are C. 

 papulosa L., and C. nordenskioldii Wagn. But C. papulosa is 

 very clearly distinguished from both, first of all, perhaps, by the 

 distinct circle of long bristles borne by the margin of each orifice. 

 Its papillae are also larger throughout and are not arranged in 

 the groups of primary and secondary ones as in our species. 



From both C. siipcrba and C. dcani, C. nordcnskioldu is distin- 

 guished superficially by its four-lobed atrial orifice ; while in its 

 internal structure it differs in possessing four gonads on each side, 

 our species possessing only one. 



All four of these species resemble one another in the posses- 

 sion of accessory dorsal languets. In C. nordcnskioldu, to judge 

 from the figure accompanying Wagner's description ('85), the 

 transverse vessels on each side end in languets, so that the 

 dorsal lamina is represented by a double row of them with a clear 

 space between. 



In C. papulosa there is a row of languets in the center of a 

 broad clear space and besides these the transverse vessels on the 

 right side end in languets, the arrangement being similar to that 

 found in C. dcani. This supplementary row of languets does 

 not appear to have been anywhere described for C. papulosa, but 

 an examination of specimens from Naples shows it to be present. 

 The Pacific coast species seem to differ from the others in pos- 

 sessing the small accessory languets scattered between two rows 

 and having no relation to the transverse vessels. This condition, 

 as pointed out in the description of the species, is but feebly de- 

 veloped in C. dcain, but much more highly so in C. supcrba. 



