App. a.] Dr. FiTTON on the Strata below the Chalk. 34:7 



Fig. 12. Lucina Portlandica. Orbicular, compressed; surface finely striated concentrically. 

 Very like Lucina concentrica, (Annales du Mus. tome vii. p. 238, and tome xii. PI. XLII. fig. 4. 

 a. h.), but much more neatly striated ; as shown by the cast of the outer surface, represented in 

 the lower figure, which is from the Isle of Portland. The upper figure is from Swindon. 



Fig. 13. Cytherea rugosa. Subtriangular; posterior extremity and beaks pointed; valves very 

 convex near the beaks ; outer surface concentrically furrowed, furrows most numerous on one side. 



Fig. 14. Trigonia incurva. (T. incurva, Benett, Wiltsh. Fossils, tab. xviii. fig. 2.) Convex, flat- 

 tened posteriorly, transversely much elongated; surface tuberculated ; width more than twice the 

 length. Since this Plate was finished, I have seen specimens from Brill, retaining the shell, which 

 is tuberculated, as in 1\ clavellata, but the tubercles are smaller. 



PLATE XXIII. 



Fig. 1. Ostrea falcata. Elongated, curved towards the posterior side; one valve flat, thick ; 

 the other unknown. 



Fig. 2. Nerita angulata. (Nerita, 2nd species ; Benett's Catalogue, p. 4.) Subglobose ? ; with 

 a single carina ; spire rather small, obtuse ; aperture oblong. This cast shows the muscular im- 

 pression very distinctly. 



Fig. 3. Natica elegans. Ovato-rhomboidal, smooth ; spire small, pointed ; whorls four or 

 five, rather angular, their uppermost edges rounded ; aperture more than two thirds of the length. 

 The shell in this specimen, whose form is well preserved in silex, is very thin and smooth. 



Fig. 4. Buccinum natico'ide. (Ampullaria elongata, Benett's Catalogue, p. 2.) Ovate, smooth, 

 thick; spire produced ; whorls four or five, their upper edges rounded, the last whorl ventricose; 

 aperture ovate, two thirds the length of the shell ; spire longer than in the last species ; shell very 

 thick. 



Fig. 5. Buccinum ? angulatum. Fusiform, short ; sides of the spire straight ; the last whorl 

 has one keel in the middle ; aperture rhomboidal, with a short rounded beak. In the produced 

 beak, this specimen approaches to the genus Fusus, but the canal appears to be too broad. The 

 external form has not been seen. 



Fig. 6. Terehra Portlandica. {Turritella, Smith, Strat. Ident. Portland-plate, fig. 2.) Tur- 

 rited, longitudinally striated ; whorls rather concave near the upper edge, where they have also 

 longitudinal furrows ; aperture acutely elliptical ; beak very short, curved. A very common 

 species in the Portland stone ; where, however, the form of the aperture is rarely seen. Here, it 

 is preserved in chalcedony. 



Fig. 7. Serpula variabilis. A cylindrical, rugose shell; with a considerable portion of the 

 tube unattached, and an irregular suture on one or more sides. When young, the attached por- 

 tion is triangular. 



Fig. 8. Serpula triserrata*. A thick, externally triangular, attached tube ; with three thin, 

 serrated keels upon the upper angle. Attached to a portion of Ostrea deltoidea. 



Fig. 9. Mya depressa, var. Oval, compressed, smooth, twice as wide as it is long. A much 

 wider specimen than that figured in Min. Conch, t. 418. Intermediate forms are also met with. 



Fig. 10. Exogyra Virgula; Goldfuss, tab. Ixxxvi. fig. 3. {Gryjjhisa Firgula, Defranee.) Much 

 elongated, arched ; one valve convex, the other concave or flat ; convex valve marked with ele- 

 vated lines; by which the species is well distinguished. 



* This specific name is substituted for " tricristata," given to fig. 8, at p. 231 ; the latter 

 having been appropriated by Goldfuss to a different species, from the lias near Bantz. — (See 

 Goldfuss, p. 226. tab. Ixvii. fig. 6.) 



