i 
1 
[ 
1888.] 148 [Meyer. 
costulata and M. Petagne only as varieties of the same species. A com- 
parison of specimens of the two recent forms, however, convinces me, 
that they are different, and this is apparently the general opinion. The 
Yorktown form agrees specifically with specimens of M. Petagne from 
Greece, and agrees in every detail with specimens of M. Petagne from 
the Canary islands. The recent M. lateralis Say, though generally stouter, 
is similar and perhaps might be united with M. Petagne. 
Modiola phaseolina Philippi. Fig. 9. 
Philippi, Enumer. mollusc. Sic., Vol. ii, p. 51, Pl. 15, fig. 14. 
Nacreous. Oblong-ovate. Ventral margin straight or subsinuated, 
dorsal margin subangulated. The small cardinal area is finely striated 
and the interior part of the dorsal margin is minutely crenulated within. 
Surface with strise of growth. 
Modiola ducatelli Conr.* from the Atlantic Miocene is 4 large, elongated 
and flattened species of apparently very different form. The type and 
only specimen has only the outside exposed so that interior characters can- 
not be determined. More similar seems to be Modiola inflata Tuomey & 
Holmes.+ But this species is founded on a single and incomplete impres- 
sion and I am unable to determine its specific characters. The Yorktown 
specimens agree with Philippi’s description and figure of M. phaseolina 
from the Crag { and with recent specimens from the coast of England. 
Semele ? virginiana n. sp. Fig. 10, 10a. 
Only the figured right valve of this form has been found. As the shell 
is solid, the adductors are well marked and the pallial line very strongly 
impressed, I think the specimen is adult, or at least adult enough to show 
its generic and specific characters. Its main peculiarity is the position of 
the cardinal teeth, which are not below the beak. Altogether I do not 
think that the shell can be properly placed into the genus Semele or any 
other existing genus, but it may be named this way until more material is 
found. It may be described in the following way. 
Minute; compressed ; not gaping. Subcuneiform, posterior side short, 
beak being rather terminal. Anterior margin regularly rounded, poste- 
rior margin truncate. Anterior muscular impression orbicular, sinuated 
anteriorly ; posterior muscular impression elongated, sinuated posteriorly. 
Pallial sinus deep. Below the small beak there is a subquadrangular car- 
tilage pit, anterior to which there is vertical and rather strong cardinal 
tooth. A second cardinal tooth adjoins it, which is obsolete, oblique and 
formed by a slight increase of the continuation of the anterior lateral 
tooth. Lateral teeth strong ; the anterior one is long, the posterior one of 
* Conrad, Mioc. Foss., p. 58, Pl. 28, fig. 2. 
+ Pliocene Foss. South Carolina, p. 88, Pl. 14, fig. 3. 
} Crag Moll., p. 59, Pl. 8, fig. 4. 
