124 - PROCEEDINGS OF THE NATIONAL MUSEUM. VOL, XXXIV. 
cluster the larger varieties of the type. The test of the genus Pene- 
roplis is a planospiral; crozier-shaped, imperforate calcareous (por- 
cellaneous) shell, and bilaterally symmetrical. An elaborate treatment 
of the genus is given by Dr. W. B. Carpenter in the Introduction to 
the Study of the Foraminifera (pp. 84-92, pl. vii). The surface of the 
shell is beautifully marked by transverse striz closely set and covering 
the entire surface, as a rule, but there are also occasional pits in the 
shell substance which resemble pores, though the shell is nevertheless 
imperforate. The genus can be well subdivided into the following 
types: 
A. Peneroplis pertusus (Forskal). Nautiloid moderately com- 
pressed, involute shell with dendritic aperture. 
B. Peneroplis planatus (¥ichtel and Moll). Broad complanate 
forms, striated surface and with a single row of pores on the septal 
face. 
C. Peneroplis arietinus (Batsch). Chambers at first involute, 
later nodosarian and numerous. Aperture a series of pores on the 
compressed anterior margin. 
D. Peneroplis cylindraceus (Lamarck). Test less compressed than 
in P. arietinus and more nearly nodosarian. 
K. Peneroplis Uituus (Gmelin). Chambers few, cylindrical, no- 
dosarian, but slightly irregular and of uneven size. 
I’. Peneroplis carinatus @Orbigny. Near variety P. pertusus but 
more involute and with sharp periphery and less decorated surface. 
G. Peneroplis levigatus. Warrer. This is the most compressed 
type, somewhat resembling Operculina adunca, and the latter whorls 
embrace nearly two-thirds of the shell. 
I find two types of the above genus, P. pertusus and P. planatus, 
the former occurring at Station 4017, the latter at Station 4694. 
PENEROPLIS PERTUSUS var. PLANATUS (Fichtel and Moll). 
Nautilus planatus FICHTEL and Mort, Test. Microse., 1808, p. 91, pl. XvI, 
AS, IL Ch; G5 Ifo 
Found only at Station H. 4694 and is rare. The genus is usually 
found at less than 30 fathoms. Tropical and subtropical waters at 
many localities. Its geological history dates from the lower Tertiary 
(Kocene of Paris Basin, etc.). 
Genus ORBICULINA. 
ORBICULINA ADUNCA (Fichtel and Moll). 
Nautilus orbiculus FicutTert and Mou, Test. Microsc., 18038, p. 112, pl. xxt. 
A tropical species usually in shoal waters. Its earliest appearance 
is in the early Tertiary. Found at Stations D. 4000 and H. 4694. 
