THE NAUTILUS. 131 



Simpson's sense. They cannot be called any more by this 

 generic name, but where they finally will land cannot be told 

 before they have been examined as to their anatomy. Already 

 Haas has separated a number of them under other generic 

 names, but these genera are mostly founded upon shell- 

 characters only. 



THE GENUS ELYSIELLA (VEREILL OE BEEGH1). 



BY SILAS C. WHEAT. 



In 1872 Prof. A. E. Verrill and Dr. Rudolph Bergh each 

 found an undescribed Nudibranch, and each erected a new 

 genus for his species. As the forms were minute and resem- 

 bled Elysia both authors chose the name Elysiella. The two 

 species have in common the respiratory sac on which Vemll 

 founded the genus, although they differ in the form of the 

 head and tentacles, on which Dr. Bergh lays emphasis. 



On the question of priority, — Prof. Verrill published his 

 genus Elysiella in the American Journal of Science for April, 

 1872 ; Dr. Bergh published his Elysiella in Heft iv. Band I, 

 Malacologische Untersuchungen in Dr. Semper 's Reisen im 

 Archipel der Philippinen. Dr. Bergh 's Band I was issued at 

 the rate of one Heft each year except in the year 1872 when 

 both Hi and iv appeared. Probably Heft iv came out in the 

 autumn of 1872, several months later than the American 

 Journal for April. A letter addressed to the publisher in 

 Germany during the second month of the present war re- 

 mains unanswered. Inquiries of American libraries for the 

 month on which they received Heft iv have brought only the 

 year 1872, copied from the title-page, not from their accession 

 records. It seems proper to credit the genus to Prof. Verrill. 



Genus Elysiella Verrill. 

 ^^ Elysiella, gen. nov. Allied to Elysia and Placobranchus. 

 Head rounded, with two short, obtuse tentacles; eyes sessile 

 behind the bases of the tentacles on the neck. Lateral lobes 

 united behind, rounded and separate in front, and raised 

 from the back, leaving a cavity beneath for respiration. 



