OSTRACODA. 659 



Eurychilina.J 



The principal peculiarity otEurychilina is the hollow area surrounding, if not all, 

 at any rate the greater part of the free margins of the valves. In PrimiUopsis, Jones, 

 a concave area occurs also, but only at the anterior end. This marginal area is not to 

 be compared with the outwardly similar " frill " of Beyrichiopsis, Jones and Kirkby, 

 nor to the "false border" of Ceratella chambersl, Ctenoholbina ciliata or Primitia dupli- 

 eata, since a distinct structure {i. e. an outer wall), wanting in those species, is required 

 to form it. Moreover, an equivalent of the "frill" is also present as a narrow 

 terminal border in most of the true species of EurycMUna. 



I say "true species of Eurychilina" because the genus as now understood 

 includes some that are not strictly in accordance with the types. Regarding, of the 

 species referred to the genus in 1890,* E. reticulata, E. subradiata, E. longula, E. 

 granosa, E. manitobmsis and probably E. cequalis is in every respect typical, we still 

 have to account for E. obesa and E.striatomarginata (Miller). After careful examina- - 

 tion I am ready to admit that these two species have not the required concave 

 marginal area. In these namely the marginal expansion is nothing more than a 

 simple border or "frill." Now, what is to be done with them? Can- they justly be 

 retained under Eurychilina ? I think not. 



In coming to this conclusion I have in mind the fact that a number of " frilled " 

 primitian Ostracoda are known that seem to stand in close relationship with E. obesa 

 and E. striatomarginata. One of these is here provisionally referred to Eurychilina 

 {E. ? subcequata) while two more are among my undescribed species from the Trenton 

 of New York. In glancing over Dr. Aurel Krause's papers on the Ostracoda which 

 he has found in the Silurian boulders contained in the drift of northern Germany, i 

 notice no less than seven species that strike me as belonging in this connection, 

 viz: Primitia distans 'Kranse, P. excavataK., P. elongata K., P. plana K., P. (Ulrichta) 

 umbonata K., Entomis flabelUfera K., and Beyrichia radians K. Of .course, if all or a 

 good proportion of these species prove to be congeneric and are -to be viewed as a 

 group by themselves and as distinct from Eurychilina, a new genus will have to be 

 established for them. I would have proposed a name in this work had I not been 

 assured of soon receiving specimens of Dr. Krause's species. When these arrive I 

 hope to enter upon a more thorough investigation of the Beyrichiidce than I have 

 yet been able to give them. 



* Jour. OIn. Soo. Nat. Hist., vol. 13, pp. 125-130. 



