﻿58 



DEVONIAN FAUNA. 



turned forward. Front wing defined. Anterior margin (omitting the front wing, 

 which is broken away) concave above, convex below. Inferior margin apparently 

 short and very convex. Contour of surface steeply convex in front and sloping out 

 flatly below and behind. Posterior wing apparently not defined. Surface bear- 

 ing about twelve large, narrow, elevated, triangular, distant ribs, extending from 

 the umbo, between which, at least on the posterior side, is a secondary series of 

 smaller and shorter ribs, and again between these a third series of still smaller 

 riblets, the whole being crossed by a few ridges of growth and possibly with a 

 finer lineation. 



Size. — About 40 mm. broad, 48 mm. deep. 



Locality. — A single defective specimen from Wolborough is in the Museum 

 of Practical Geology. 



Ji'rniKii-s. — This evidently is a distinct and fine species belonging to the true 

 Pterineae of the group of Pt. costata, Goldfuss, 1 as defined by Freeh. 2 Our solitary 

 example is unfortunately too defective to permit a full description. Its anterior 

 wing is gone, the margins can only be approximately traced, and the surface has 

 lost its finer ornamentation. The posterior portion is obscured by matrix, but 

 it appears to have been considerably produced, so as to form a large undefined 

 hind wing with few and coarse ribs. 



Affinities. — It so closely resembles Pt. dichotoma, Krantz, 3 as in the defective 

 state of our specimen to admit the question of its identity. It appears, however, 

 to have fewer and more definitely alternating ribs, and a much less defined hind 

 wing, which, as far as seen, shows no signs of fine radiations. Freeh's 4 version 

 of that shell approaches it more nearly in shape, but still differs in the same 

 particulars. 



Pt. fasciculata, Goldfuss, 5 differs in its greater obliquity, its more evenly 

 rounded back, its flat defined hind wing, its numerous equal minor strise between 

 the major ribs, and its smooth cast. Freeh, 6 however, disagrees with Goldfuss 

 in describing its major ribs as alternating. 



Pt. costulata, F. A. Romer, 7 is distinguished by having its ribs nodu- 

 lous. 



1 1831-iO, Goldfuss, ' Petrel'. Germ.,' vol. ii, p. 137, pi. exx, iig. 4. 



2 1891, Freeh, 1 Abhandl. Geol. Speeialk. Preusss.,' Band 9, pt. 3, p. 81. 



3 1857, Krantz, ' Verband. n. Vereins preuss. Rheinl.,' vol. xiv, p. 157, pi. xi, fig. 5. 



4 1891, Freeh, 4 Abhandl. Geol. Speeialk. Preuss.,' Band 9, pt. 3, p. 88, pi. ix, fig. 16. 



5 1834-40, Goldfuss, ' Petref . Germ.,' vol. ii, p. 137, pi. exx, fig. 5; and 1853, Sandberger, 

 ' Verst. Rhein. Nassau,' p. 293, pi. xxx, fig. 7. 



fi 1891, Freeh, ' Abhandl. Geol. Speeialk. Preuss.,' Band 9, pt. 3, p. 84, pi. viii, figs. 1, la; and 

 pi. ix, figs. 1 — 3. 



7 1850, F. A. Earner, ' Beitr.,' pt. 1, p. 3, pi. i, fig. 3. 



