I6i 



CONOHIFERA. 



Gervillia. 



above, protruding in a lengthened sharp point, and consider- 

 ably concave on the margin ; surface with six elevated, narrow, 

 longitudinal, divergent ribs, extending beyond the margins, 

 and acutely pointed ; the central, second, and sixth ribs being 

 higher than the others, which are intermediate ones ; the rib 

 next the larger ear is invariably tripartite ; the intercostal 

 spaces with fine, irregular, longitudinal stria) ; crossed towards 

 the base with lines of growth ; margins between the ribs con- 

 vex ; flat valve, with the hinge-line quite straight, the anterior 

 auricle corresponding with that of the lower valve ; the larger 

 one undefined, acute above, and much less concave on the 

 margin than that of the other valve ; surface with five or six 

 longitudinal divergent furrows, corresponding with the ribs in 

 the opposite valve, the intermediate spaces with numerous, 

 fine, longitudinal strise ; margins plain and quite circular. 



The Lias, Saltford, near Bath. 



Althougli Mr Stutchbury's figure is scarcely two inches in length, the 

 ribs protnide six-eighths of an inch beyond the margins. 



Genus XXV.— PTERINEA— GoW/«w. 



Shell equivalve, inequilateral, both sides furnished with 

 lateral auricles ; the anterior one short ; the posterior distinctly 

 defined ; hinge area broad and lengthened, its superior margin 

 straight, and the surface generally with a series of parallel 

 lines ; ligament internal ; hinge with several oblique cardinal 

 teeth, situate below the beaks, and with one or more lateral, 

 very oblique, remote teeth, sloping considerably downwards 

 from the umbones to the anterior side, with one large muscu- 

 lar impression in each valve. 



The shells of this genus may easily be mistaken for those of 

 Avicula, where the inside of the valves are hidden from view. 

 1. Pterinea ventricosa. — The Inflated Pterinea, pi. 

 LXI.** figs. 16, 17. 



P. ventricosa. Goldfuss, pi. 119, fig. 2. Phillips, Pal. Fos. 

 p. 4.9, pi. 22, fig. 82. 



Much and obliquely elongated, its length more than double 

 its breadth ; ventricose ; hinge-line straight and slightly ob- 

 lique ; auricles unequal, the anterior ones very small and 

 acuto, the other very large, extending below the centre of the 

 side ; beaks obtuse ; hinge with oblique narrow teeth, gradu- _ 

 ally lengthening posteriorly, forming a triangular series, with 

 a series of shorter teeth behind them; surface smooth. 



The Devonian Shales, Newton Bushel. 



2. Pterinea radiata. — The Rayed Pterinea, pi. LXI.** 

 fig. 22. 



P. radiata. Goldfuss, pi. 119, fig. 7. 



Transversely oblong ; surface with a series of wide-set lon- 

 gitudinal, rounded, divergent ribs, with one or two intervening 

 ones between each, the whole surface crossed by numerous 

 waved strife ; margin scolloped. 



The Devonian Shale, Newton Bushel. 



3. Pterinea spinosa. — The Spinous Pterinea. 



P. spinosa. Phillips, Pal. Fos. p. 48, pi. 22, fig. 8. 



Oblique ; deeper valve very convex along the middle, as 

 well as the anterior, which is small, rounded, and separated 

 from the middle by a deep, broad sinus, and depression ; ante- 

 rior side expanded and flattened ; whole surface with large, 

 lungltudinal, wide-set, oblique ribs, which are provided with 



imbricated, distant spines, and crossed by fine concentric 

 strioB ; on the disks the intercostal spaces are flat, longitudi- 

 nally striated, as also the posterior wing. 



Devonian Shale, Petherwiu. 



4. Pterinea Thompsoni. — Thompson's Pterinea. 



P. Thompsoni. Portlock, Geo. Rep. p. 431, pi. 25 A, 

 fig. 10. 



MHich elongated transversely ; convex ; body of the shell 

 oblique ; hinge-line quite sharp and horizontal, extending the 

 entire length of the valve, terminating on both sides with 

 lengthened acute auricles, with a slight contraction under the 

 anterior one ; the posterior margin sigmoidal ; beak not ex- 

 tending beyond the hmge-line. 



The Carboniferous Limestone, Tyrone, Ireland. 



Figs. 3fi and 37 represent Pterinea Iwvis, to shew the teeth of another 

 division of the genus. 



Genus XXVI.— MONOTIS.— 5ro«»i. 



Sub-equivalve, inequilateral sub-orbicular ; compressed ; 

 close ; anterior auricle small, with a larger continuous one on 

 the posterior side ; hinge-line straight, thick, and destitute of 

 teeth ; beaks depressed and sub-medial, with a canal below 

 them in front, inclining in the right valve, and a plait 

 within. Muscular impressions unknown. 



1. MoNOTis deccssata. — The Decussated Monotis, pi. 

 LXL** figs. 18, 19. 



M. (lecussata. Goldfuss, pi. 1 20, fig. 8. 



Sub-orbicular ; under valve convex, the other rather fiat ; 

 hinge-line straight and horizontal ; auricles not refined ; umbo 

 rounded and blunt ; surface with numerous fine, divergent 

 ribs, thickly beset with imbricated spines, the intercostal spaces 

 with fine longitudinal stri.T, crossed by numerous flat, broad 

 stria; ; margins scolloped ; upper valve with a large posterior 

 auricle, hollowed on the side, and defined by four radiating 

 ribs ; the anterior side with a small acute ear, separated be- 

 low by a notch ; from the umbo emanate numerous undulating, 

 divergent, irregularly-set ribs, which occupy the central por- 

 tion of the valve, leaving a space destitute of ribs on both 

 sides ; the intercostal spaces with numerous shallow, concentric 

 grooves, which cover the whole surface. Length six-eighths 

 of an inch ; breadth somewhat less. 



The Lias, Gloucestershire. 



Fig. 20 repsesents the hinge of Monotis suhcostata. 



Genus XXVII.—GEiiVILLIA.—i>e/>a«c«. 



Shell oblong, nearly equivalve, greatly inequilateral, and 

 oblique ; hinge-line rather long, linear and nearly straight, 

 with several irregular, somewhat transverse, small pits, for 

 the reception of the ligament ; teeth numerous, more or less 

 lamelliform, interlocking, variable in direction and size, situ- 

 ate below the dorsal edge ; each valve with one muscular im- 

 pression. 



1 , Gervillia solenoides. — The Solen-shaped Gervillia, 

 pi. LXIX. fig. G. 



G. solenoides. Sowerby, VI. p. 14, pi. 510, figs. 1, 2, .3, 4. 



Greatly elongated transversely, its width being nearly eigiit 



