134 THE NAUTILUS. 



as we know pass Point Concepcion, Many other examples might 

 be noted. 



This is not the place to enter into a discussion of the West Coast 

 marine faunal provinces. But it is interesting to note that as far as 

 the material at hand gives evidence, the two AVest Coast species of 

 Nuttallina are sharply divided by this natural boundary. At Carpin- 

 teria, ten miles east of Santa Barbara and at points west of that town, 

 to Santa Anita, within ten miles of Point Concepcion, the specimens 

 are uniformly N. scabra, as are also the more southernexa mples of 

 the genus. Specimens collected at Point Sal, thirty-five miles north- 

 ward from Point Concepcion, together with those collected at San 

 Simeon, at Monterey, at Purissima and at points near San Fran- 

 cisco are uniformly N. californica. No intregrading forms were 

 observed. While the external appearance is not always a sure 

 guide to specific position, disarticulation of the plates has, in all 

 cases examined, revealed the species with certainty. 



A study of numerous specimens from the localities mentioned, 

 shows the following differential characteristics, in addition to those 

 cited by Mr. Pilsbry. Whether they would hold good in sj)ecimens 

 from other localities or not, I do not know. In color N. scabra is 

 externally more varied than N. californica. Specimens of the former 

 from Santa Barbara are clouded and mottled with greenish upon a 

 buff ground-tint, on the second, third, fifth and sixth valves. The 

 remaining valves are much darker and less variegated. In single 

 valves of 5ca6ra, viewed from above, the broad curving outline of 

 the tegmentum on each side is bordered by a small spot of brown, 

 placed centrally on the light blue surface of the sutural plates. This 

 feature is constant in all of the specimens examined. In N. cali- 

 fornica the spots are wholly absent, or in some cases replaced by in- 

 distinct clouds of a color darker than the surface of the sutural 

 plates. Of course no one would se])arate the species because of these 

 slight color differences, but taken in conjunction with the weightier 

 points of difference furnished by the shape of the plates, sculpture 

 and character of the gii'dle, they are interesting as showing how far 

 these geographical races have become differentiated from the parent 

 stock. 



