NO. 2124. TEE WEST AMERICAN SPECIES OF NUCELLA—DALL. 561 



cavely arched, and there are occasionally from three to eight obscure 

 denticulations within the outer lip. The colors range about the same 

 as in the other species, but there seem to be fewer light colored and 

 more melanitic specimens. The proportion of unicolored individuals 

 is markedly less. 



The operculum throughout the group has the usual characters 

 belonging to the genus. It seems to be rather larger, in proportion to 

 the aperture, and perhaps generally darker in color in N. emarginata 

 and smaller and paler in N. lamellosa than in the other two species. 



Thinking that the major spirals might afford some specific charac- 

 ters, aU the specimens in the collection were subjected to a careful 

 count, 1,753 in all. The count was taken at the end of the penulti- 

 mate whorl from the commissure of the outer hp with the body whorl 

 to the suture behind. Only adult specimens were included in the 

 count. 



Of 529 specimens of N. emarginata 433 had two, 78 had only one, 

 and 18 had three major spirals. The intercalary spiral threads in 

 the whole space between the sutures varied from none to three, 290 

 specimens having none, 118 having one, 109 having two, and 12 

 having tliree. 



Of 315 specimens of N. lima 110 had three major spirals, 130 had 

 four, 71 had five, 2 had six, and 2 had seven. Of intercalary threads 

 two had none, 135 had three, 114 had four, 31 had five, and 3 had six. 



Of 363 specimens "of iV. canaliculata 27 had three major spirals, 135 

 had four, 136 had five, 63 had six, 1 had seven, and 1 had eight. Of 

 intercalary threads, 112 had none, 6 had one, 43 had two, 57 had 

 three, 78 had four, 56 had five, 7 had six, and 4 had seven. 



Of 549 specimens of N. lamellosa 32 had one major spiral, 417 had 

 two, 4 had three, and 2 had four. On the last whorl 368 had nine 

 major spirals and the others varied from one to thirteen. 



Of 21 specimens of N. freycinetii 18 had two major spirals and the 

 others three. The interoalaries -varied from two to five ; but the num- 

 ber of specimens being so restricted, the result in this case is not 

 conclusive. 



If these figures for the major spirals be platted, it will be evident 

 that the profile of the curve for each species has its own character- 

 istics, and it is quite possible that the few scattering exceptions to 

 the rule may be due to hybridization. 



The species of Nucella are in the main carnivorous, and have been 

 observed by me to feed on small bivalves hke Anomia, on Ascidian 

 colonies, and on the ovicapsules of their own and other species of 

 gastropods. In scraping off other small invertebrates from kelp and 

 rockweeds it is probable they swallow a certain amount of vegetable 

 matter, and on one occasion I found several feeding on the rather 

 putrid body of a dead fish. Yet I have never observed them attack- 



81022°— Proc.N.M.vol.49— 15 36 



