PLATE LXI.*** 
1. Posidonia Anodontoidea. (Anodon-shaped Posidonia.) Transversely oblong-ovate; liinge-line curved; umbones 
obtuse ; surface, with many, narrow, concentric ridges. 
2. P. Lateralis. (Lateral Posidonia.) Transversely elongated, oblong-ovate, oblique, compressed ; beaks near anterior 
extremity; surface, with concentric, angular ridges. 
3. Perna Rugosa. (Rugged Pema.) S ub-quadrate; liinge-line oblique; area, with eighteen or nineteen, parallel 
grooves ; beaks acute, with lunular excavation beneath ; surface, with many, concentric lines of growth. 
4. Crenatula Ventricosa. (Bellied Crenatula.) Ovate, gibbose, ventricose, carinated; hinge-line short; posterior 
side compressed; anterior side rounded; interior pearlaceous. 
5. C. Listeri. (Lister’s Crenatula.) Elongated; hinge-line oblique; crenulations large; valves narrow above, wide 
below. 
6. 6*. C. Producta. (Produced Crenatula.) Elongated; liinge-line oblique, with four, large crenulations; beaks 
prominent; basal margins of valves produced ; external surface, with concentric lamina?. 
7. Hinge of Crenatula Ventricosa. 
8,9. Catillus Crispii. (Crisp’s Catillus.) Obovate, compressed, with many, transverse ridges; beaks acuminated; 
posterior side small, depressed ; anterior side expanded ; hinge-line oblique. 
10. C. Lamarckii. (Lamarck's Catillus.) Valves equal, convex, with obscure, longitudinal undulations and transverse 
ridges; surface, with many, concentric stria?; posterior side sub-compressed; anterior side lobate, expanded; liinge-line 
transverse. 
11, 12. Modiola Amyg’dalina. (Almond-shaped Modiola.) Elliptical, gibbous; beaks close to anterior side, incurved 
over excavated, small lunule ; surface, with fine, concentric stria?. 
13. M. Expansa. (Expanded Modiola.) Elongated; liinge-line straight; rounded and narrowed anteriorly; expanded 
posteriorly, with oblique, curved truncation. 
14, 15, 16. M. Macadami. (Macadam's Modiola.) Lengthened, narrow, convex, cylindrical; beaks obscure ; front 
rounded ; hinge-line straight; surface, with fine, concentric stria?. 
17. M. Nerei. (Nere's Modiola.) Obovate, convex, thick ; beaks terminal; sides equal, curved; hinge-line straight; 
surface, with fine, regular stria?. 
18. M. Subparallela. (Sub-parallel Modiola.) Oblong-ovate, convex; beaks obtuse; liinge-line straight; with a 
diagonal rise from beak to margin; surface, with irregular, concentric striae. 
19. 20. M. Carinata. (Keeled Modiola.) Ventricose, boat-shaped; valves deep; beaks obtuse; with abrupt, carinated 
ridge from beaks to posterior, lower angle of valves; surface, with a few lines of growth. 
21. Trig’Onia Literata. (Lettered Trigonia.) Sub-triangular, sub-conic, convex; anterior side sub-truncated ; posterior 
side acuminated below, with longitudinal, linear row of tubercles; anterior portion of surface, with series of rugged ribs, 
which at centre of valve turn upwards at an acute angle in form of letter V; ribs, crossed by rough stria?; beaks 
acuminated ; lunule large; basal line convex. 
24, 25, 25*. Pleurodon Ovalis. (Oval Pleurodon.) Ovate, deltoidal, gibbose, sub-orbicular; smooth ; margin entire* 
hinge, with five or six cardinal teeth, and one lateral tooth in each anterior side of valves. Diameter, A in * 
26. Maerodon RugOSUS. (Rough Macrodon .) Transversely elongated; surface and margin flexuous; extremities 
truncated; surface, with many, concentric lines of growth; sulci with strong, prominent, radiating ribs; basal line 
undulating. 
27. Astarte Obliqua. (Oblique Astarte.) Gibbose, transversely obovate; anterior side truncated; lunette concave, 
heart-shaped; surface, with many, small, concentric ridges; edge broad, flat, crossed by sulci; shell thick. 
28. Lysianessa Rhombifera. (Rounded Lysianessa.) Ovately trapeziform ; narrow in front; obliquely truncated 
posteriorly; beaks sub-central; ribs angulated, truncated, recurved. 
29. PleurorhynchllS Elongatus. (Elongated Pleurorhynchus.) Transversely elongated; ventricose; anterior side 
conical; posterior side short, inflated; surface, with many, radiating stria?. 
( 70 ) 
