OSTRACODA. 659 
Eurychilina. | 
The principal peculiarity of Hurychilina is the hollow area surrounding, if not all, 
at any rate the greater part of the free margins of the valves. In Primétiopsis, 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 chambersi, Ctenobolbina ciliata or Primitia dupli- 
‘cata, since a distinct structure (/. 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 Hurychilina. 
I say “true species of Hurychilina” 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,* KH. reticulata, EH. subradiata, E. longula, E. 
granosa, Ij. manitobensis and probably HE. wqualis is in every respect typical, we still 
have to account for H. 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 Hurychilina? 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 EH. striatomarginata. One of these is here provisionally referred to Hurychilina 
(H.? subequata) 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, | 
notice no less than seven species that strike me as belonging in this connection, 
viz: Primitia distans Krause, P. excavata K., P. elongata K., P. plana K., P. (Ulrichia) 
umbonata K., Entomis flabellifera 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 Hurychilina, 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 Beyrichiide than I have 
yet been able to give them. 
* Jour. Cin. Soc. Nat. Hist., vol. 13, pp. 125—130. 
