236 MESSRS. BRADY, PARKER, AND JONES 
POLYMORPHINA HuMBOLDTIL, Bornemann. (Plate XL. figs. 21, a, b.) 
Polymorphina Humboldtii, Bornemann, 1855, Zeitschr. deutsch. geol. Gesell. vol. vii. p. 347, pl. 18. 
figs. 7, 8; Reuss, 1866, Denkschr. d. math.-natur. Cl. k. Akad. Wissensch. vol. xxv. p. 155; Gümbel, 
1868, Abhandl. d. ii. Cl. k. Akad. Wissensch. vol. x. p. 647. 
Characters.—Shell oval or oblong, inequilateral, compressed; one side flat, or some- 
times slightly concave, the other surface convex. Anterior extremity acute; posterior 
rounded. Margins thin, often spreading into an obtuse carina. Chambers long, narrow, 
oblique, curved, slightly inflated ; arranged with some € in two set ex series. 
Orifice pouting, radiate. Surface smooth. Length ¿5 to yẹ inch. 
In the absence of specimens from which to form an independent judgment, we are Qui 
ready to accept Polymorphina Humboldtii, represented in Dr. Bornemann's figures, as 
a good subtype. The drawings indicate a compressed, carinate, Textulariform test, 
bearing near relationship in the arrangement of its chambers to P. complanata, but 
rounder and more elegant in its lines and unequal in its two sides. 
Distribution. —P. Humboldtii was first described from specimens obtained in the Sep- 
taria-clay (Lower Tertiary) of Hermsdorf, near Berlin ; and though this formation has been 
thoroughly examined in many localities widely separated, it has not been noticed at any 
other portion of it. Dr. Gümbel's note refers to specimens of somewhat earlier age, the 
Eocene of the Northern Alps. 
POLYMORPHINA CONCAVA, Williamson. (Plate XL. figs. 22, a, b.) | 
Polymorphina lactea, var. concava, Williamson, 1858, Rec. For. Gt. Br. p. 72, pl. 6. figs. 151, 152. 
Characters.—Shell irregular, oval or oblong, eoncavo-convex; at some period of its 
growth parasitic. Central portion consisting of a small hyaline shell of the typical form, 
round which the last segment is extended as a thin, arched, marginal expansion. On the 
under or concave surface the earlier segments are scarcely visible. Margin very thin, 
rounded, sinuous. Surface smooth. 
Professor Williamson's figures, from which our own are copied, are the only previous 
record we find of unmistakably parasitic Polymorphine, and they agree with specimens 
which have come under our own notice. In the present memoir we describe a second 
attached variety (see p. 246), in which cervicorn shelly growths serve to root the animal 
to a foreign body. We propose, notwithstanding certain points of similarity between the 
two, to limit Prof. Williamson's name to the more | regularly formed variety which he 
describes. 
It is not easy to read the physiological significance of the oubeprind ultimate ell 
which characterizes Polymorphina concava. It has no visible orifice, and is, in fact, 
only a wide inequilateral ring round the long periphery of the shell; and in well-pre- 
served specimens the orifice of the penultimate chamber remains large and conspicuous. 
It may be that the supplementary closed-in segment bears a direct analogy to the closed 
tubular eae often observable in P. Orbignii.. 
ion.—P. concava is extremely rare, and probably ies not been noticed Be 
