60 PROCEEDINGS OF THE ACADEMY OF 



ably in form and surface markings, some of the specimens being proportion- 

 ally more ventricose, or, in other words, have the body volution, and conse- 

 quently the aperture, higher in proportion to breadth than the others, 'while 

 more or less difference in the elevation or depression of the spire is observ- 

 able. The most marked differences, however, are to be observed in the char- 

 acter of the surface markings. Generally the little regular costse parallel to 

 the lines of growth are pretty well defined, but in some cases they fade away 

 so as to be scarcely distinguishable from the fine incremental lines; while in 

 others they are strongly marked, regularly disposed costas. Sometimes, dif- 

 ferent parts of the surface of the same individual specimen present the varia- 

 tion of sculpturing mentioned. It may be found convenient to designate the 

 more ventricose form as variety ventricosa. 



Named in honor of G. W. Tryon, Jr., of Philadelphia. 



Locality and position. Same as last. 



Carinipex (Tryoni, var.) concava, Meek. 



The only two specimens of this form obtained are considerably smaller than 

 the adult size of the last described species, and differ in having the spire so 

 strongly depressed as to be really concave, and thus to give the entire shell a 

 subplanorbicular outline. Its umbilicus is proportionally of about the same 

 size, as in the C. Tryoni, and its two or three volutions, as in that form, are 

 rounded and without carinse. Its aperture is more nearly circular, being 

 about as wide as high, in consequence of the body volution being proportion- 

 ally less prominent below. Its costae are very strongly defined and regularly 

 disposed. 



It seems improbable that this can be merely the young of C. Tryoni, because, 

 of some forty odd specimens now before me, not one has the apex or first 

 two volutions concave, though they vary somewhat in prominence in differ- 

 ent individuals. 



Height, 0-18 inch ; breadth, 0-30 inch ; height of aperture, 0-18 inch ; breadth 

 of do., 0-17 inch. 



Locality and position. Same as foregoing. 



Devonian Species. 

 Spirifer (Trigonotreta) Pinonensis, Meek. 



Shell attaining about a medium size, somewhat wider than long, varying 

 from transversely subovate to a nearly semicircular general outline ; rather 

 gibbous in adult examples ; cardinal margin nearly or quite equaling the 

 greatest breadth, and terminating in rectangular or rather more obtuse extre- 

 mities ; lateral margins rounding to the front, which is sometimes rounded, 

 sometimes slightly sinuous, or in other examples more prominent and suban- 

 gular in the middle. Ventral valve generally rather more gibbous than the 

 other, its greatest convexity being in the umbonal region, from which it rounds 

 off evenly toward the front and lateral margins, as well as to the beak, which 

 projects beyond that of the other valve, and is rather distinctly incurved ; 

 cardinal area of moderate height, narrowed to the lateral extremities, more or 

 less inclined backward, and strongly arched with the beak ; foramen having 

 nearly the form of an equilateral triangle, and provided with slightly raised, 

 sharp lateral margins; mesial sinus shallow, rounded, smooth, and of mode- 

 rate breadth narrowed regularly, and well defined to the apex of the 

 beak. Dorsal valve generally more than semicircular, most convex in the 

 central and anterior regions; beak projecting little beyond the cardinal mar- 

 gin, and with the narrow area incurved; mesial ridge depressed, smooth, 

 and faintly furrowed along the middle, corresponding in outline to the form of 

 the sinus in the other valve. Surface of each valve ornamented by from 

 eleven to about fourteen simple, regular, rounded, radiating plications on each 

 side of the mesial fold and sinus, and also showing, under a magnifier, minute, 

 regular, crowded radiating stria?, crossed near the front by stronger undulating 

 lines of growth. 



[April, 



