UNIVERSITY OF CALIFORNIA PUBLICATIONS 

 ZOOLOGY 



Vol. 3, No. 6, pp. 93-116, Pis. 15-17 December II, 1906 



CONTEIBUTIONS FKOM THE LABOEATOEY 



OP THE 



AIAKINE BIOLOGICAL ASSOCIATION OF SAN DIEGO. 



XIII. 



DINOFLAGELLATA OF THE SAN DIEGO 



REGION, II. ON TBIPOSOLENIA, A NEW 



GENUS OF THE DINOPHYSIDAE. 



BY 



CHAELES ATWOOD KOFOID. 



The plankton taken in deeper waters off San Diego during 

 the past four j-ears has contained a number of individuals of 

 species of the Dinophysidae related to Amphisolenia. The rela- 

 tive variety of the forms and their less accessible habitat prob- 

 ably account for the fact that they have not been observed by 

 other investigators, though it is not improbable that Sehiitt's 

 ('93) Amphisolenia tripos {nomen nudum) is a member of this 

 genus. 



The five forms here described, together with three others de- 

 scribed elsewhere (Kofoid :06), constitute a compact group of 

 related species having in common a set of distinctive characters 

 which delimit them from the known species of Aniphisolenia, to 

 which genus they are all more closely related than to any other of 

 the Dinophysidae. 



Their relationship to Amphisolenia is indicated by the differ- 

 entiation of the body into the following regions : An expanded, 

 rounded, or flattened head girdled by the transverse furrow, an 

 elongated slender neck terminating posteriorly in the expanded 

 cytopharynx, an expanded midbody containing the nucleus, and 



