26 
MUSEUM BULLETIN No. 31. 
name for those species which had the interior structure of a Tri- 
plecia but with a striated or plicated exterior. This was done in 
ignorance of the fact that Prof. Foerste had already suggested the 
subgeneric term Cliftonia for a new species which he called Cliftonia 
striata 1 . ( * 
It is doubtful if all the species of striated Triplecias belong to the 
same sub-genus. In fact, the presence of a long, bifurcated cardinal 
process cannot be taken as a positive guarantee of relationship. Such 
a process is known in brachiopods that no one would ever think of 
classing with Triplecia. 
CUftonia striata Foerste and Cliftonia? ienax Foerste are both 
unlike all the other striated Triplecias in external appearance. Clif- 
tonia striata , the type, is, of course, the only one which is here con- 
sidered. This species is described as resembling a email Atrypa, 
whereas all the other striated Triplecias are comparable to Platystro- 
phia; it is nearly circular in outline, whereas other species are dis- 
tinctly wider than long; the fold is very low and the sinus shallow, 
but in other species the fold and sinus are prominent features. 
Professor Poerste evidently did not intend to include in this new 
subgenus all the striated and plicated Triplecias, for he makes no 
mention of the Ordovician species and says “Possibly Triplecia nia- 
garensis Hall and Clarke, is congeneric”. Triplecia niagarensis is 
one of the more typically Platystrophia-like forms. 
In Triplecia ulrichi , T. niagarensis , and Oxoplecia calhouni , the 
cardinal process stands erect, and turns somewhat backward, into 
the umbo of the pedicle valve. Poerste does not figure the cardinal 
process of Cliftonia striata, but says in his description: “Interior of 
brachial valve with a lingulif orm cardinal process 1 -7 mm. in length, 
and 0*75 mm. in width at the hinge line. This process becomes broader 
anteriorly, and divides near the top into two short, sharply pointed, 
divisions.” In describing the cardinal process of Oxoplecia one might 
say upward or posteriorly, but not anteriorly. It might he inferred 
from this that the cardinal process- of Cliftonia projected forward into 
the valves, which is a position unlike that in any of the Platystrophia- 
shaped Triplecias. 
The writer does not believe the identity of Cliftonia and Oxo- 
plecia can he demonstrated, and will, therefore, use the term Oxoplecia 
for the striated or plicated Triplecias like 0. calhouni Wilson, T. 
ulrichi Ulrich and iSchuchert, T. niagarensis Hall and Clarke, and 
Or this insularis Eichwald. 
i Bull, Denison Univ., 14, p. 82, PI. 3, figs. 39, 42, PI. 4, fig. 70, Apr. 1909. 
