A pp. A.] Dr. FiTTON on the Strata helom the Chalk. 335 



APPENDIX. 



APR A. 



Descriptive Notes respecting the Shells figured in Plates XL to XXIII. 

 By James de Carle Sowerby, F.L.S. &c. 



PLATE XI. 



Fig. 1. Tornatella elongata. Elliptical, elongated; surface furrowed; furrows crossed by 

 short lines ; whorls about four ; lip slightly thickened. This resembles Acteon {Tornatella) simu- 

 latus (Min. Con. 1. 163. f. 2.) of the London clay, even in the dotted furrows upon the surface of 

 the shell, but it is much longer in proportion, and is only half the size. 



Fig. 2. Lucinal glohosa. A nearly globose smooth shell, with the lines of growth peculiarly 

 waved near the posterior margin. I have not seen the interior. 



Fig. 3. Avicula Gryphceoidcs. The convex valve nearly orbicular, with a projecting incurved 

 beak, and two small unequal ears : when alone, it may easily be mistaken for Inoceramus con- 

 centricus, but the parts about the beak, especially the ears, show the difference. The other valve is 

 nearly flat, orbicular, and has one small and one large ear. The convex valve a. is represented 

 from specimens found at Nursted in Hampshire ; the other valve, b. is from Cambridgeshire. 



Fig. 4. Pentacrinus. The stem only has yet been found ; it is various in size, the sides are 

 concave, the angles rounded. Joints equal, the margins of their surfaces ornamented with short 

 striae. Some specimens show the bases of lateral arms. It strongly resembles a species found in 

 the chalk ; — (Mantell ; Fossils of the South Downs, p. 183; Geol. of the S.E, of England, p. 112.); 

 which is, however, much larger. 



Fig. 5. PoUicipes Icevis. The lateral valves are rhomboidal, smooth, thin, and nearly flat : in 

 the partially decomposed state in which they are found, they appear to be composed of layers, of 

 different degrees of transparency and depths of colour. This species also occurs in the green- 

 sand at Blackdown: see Plate XVI. fig. ]. 



Fig. 5*. PoUicipes unguis. Smooth, the valves are all remarkably curved, and broad in pro- 

 portion to their length. 



Fig. 6. PoUicipes radiatus. Valves wedge-shaped, flat, marked with sharp, elevated rays, di- 

 verging from their apices. 



Fig. 6*. PoUicipes rigidus is distinguished by thin transverse elevations, which are very promi- 

 nent upon the posterior valves : the lateral valves are elongated. 



Fig. 7. Venus'? tenera. Shell lenticular, rather transverse, neatly marked with concentric 

 striae ; lunette lanceolate. 



Fig. 7*. Venericardia tenuicosta. Transversely oblong, approaching to square. It varies 

 much in convexity : and when old or interrupted in its growth, is nearly globose, rather heart- 

 shaped. Specimens have been found twice the length of that represented in the figure, both 

 of the oblong and globose form. The surface of the rays is rough, with slightly elevated obtuse 

 scales. The interior of the margin is crenated. Lunette rather deep, heart-shaped. 



Fig, 8. Nucula hivirgaia. Very convex; the surface ornamented with two sets of linear 

 furrows, which meet towards the posterior slope, at acute angles directed towards the beak of each 

 ▼alve ; the juiuition producing a regular line, without forming a ridge. Lunette broad. 



VOL. IV. SECOND SERIES. 2 X 



