Ihe Nautilus. 



Vol. XXX. MAY, 1916. No. 1 



NOTES ON THE CALIFORNIAN SPECIES OF ADULA. 



BY WILLIAM HEALEY DALL. 



The genus Botula was proposed by Morch. in 1853, in the 

 second part of the Yoldi catalogue, page 55, for Modiola vagina 

 Lamarck and M. fusca Gmelin, the latter better known as M. 

 cinamomea Lamarck. 



The former seems not to differ materially from the typical 

 Modioli except in its less arcuate form, and the latter by its 

 small size, incurved umbones and boring habit must be relied 

 on to carry the genus if it is valid. The group now under con- 

 sideration differs but little from Botula so typified, the species 

 grading from one to another so as to nearly bridge the gap be- 

 tween Botula and Ldthophaga. It can hardly rank higher than 

 a subgenus at most. 



The subgenus Adula was proposed by the brothers Adams in 

 December, 1857, in their "Genera of Recent Mollusca," for the 

 single species Mytilus soleniformis of Orbigny, 1846, from Payta, 

 Peru. 



The generic name was used again in 1861, by Henry Adams 

 for a Planorbis, probably by inadvertence. 



The typical species of Adula differs from those of the California 

 coast by having more nearly central umbones, if Orbigny' s fig- 

 ure can be relied upon. 



The earliest of the Californian species to be noticed was : 



