EXPLANATION OF PLATES. 439 
FIGURE, PAGE, 
25, 26. Hippurites radiosus, Desm. 25. Interior of lower 
valve, 4. 26. Upper valve (restored). Lower Chalk; 
St. Mamest, Dordogne. a,a, adductor impressions 
and processes; c,c, cartilage pits; ¢, t’, teeth and 
dental sockets; uw, umbonal cavity; p, orifices of 
canals; /, ligamental inflection; m, muscular, n, 
siphonal inflection, . : . 204 
27, 28. Hippurites Toucasianus, VOrb. 27, Upper valve, 4. 
28. Lower valve, with mould ; 1, ligamental, m, mus- 
cular, ”,siphonal inflections; , fracture, showing 
canals; ¢, cartilage; wu, left umbo; the arrows indi- 
cate the probable direction of the. branchial currents, 203 
‘29, 30. Hippurites sulcatus, Defrance. Cret.; France, . 203 
31. Radiolites alata, d’Orb., : ° % : . 205 
32, 33. Radiolites mammillaris, Math., 4. 32. Interior of 
lower valve. 33. Interior of upper an L. Chalk; 
S. Mamest, Dordogne. J, ligamental inflection; m, 
pallial line; c,c, cartilage pits; a@,a,adductor impres- 
sions and processes; ¢, teeth and dental sockets,  . 205 
34, 35. Radiolites mammillaris, Math. Side views of the 
upper valve. J, ligamental inflection; ¢, teeth; a,a’, 
muscular processes, ‘ : : : P . 205 
36, 37. Radiolites Heeninghausii, Desm. One-half size. 
Chalk. 36. Upper, 37. Side view. uw, umbo of left 
valve; r, right umbo; J, ligamental groove; ¢,c, °. 
cartilage ; a, anterior adductor muscle; a’, posterior, 205 
38. Biradiolites canaliculatus. p, point of attachment; J, 
ligamental groove; a, a, corresponding areas, . . 206 
39. Spheerulites unisulcatus, Matheron,  . . : . 206 
PuateE 119. 
40. Lucina Jamaicensis, Linn. West Indies, . : . 210 
41. Lucina (Cyclas) divaricata, Linn. West Indies, . 210 
42. Lucina (Codakia) tigerina, Lam. West Indies, . 210 
43. Lucina (Miltha) Childreni, Gray. Brazil, : . 210 
44, 45. Lucina (Myrtea) secabra, Lam. California, . . 210 
46, 53. Lucina (Here) Richthofeni, Gabb. Tert.; Cal. . 210 
Aq. Loripes edentula, Linn. West Indies, ; i - O00 
48, Cryptodon flexuosus, Montf. England, : ‘ a Zk 
49, 50. Philis Cumingii, Fischer. Moluccas, . - . 211 
51. Corbis fimbriata, Linn. Fiji Islands, . . 212 
52. Corbis (Sphera) corrugata, Sowb. Neocomian; ‘Eur., 212 
54. 55. Corbis (Spheeriola) Mellingi, Hauer. Tri jas: Eur., 213 
56. 57. Corbis (Mutiella) coarctata, Zitt. Turonian; Gosau, 212 
58. Unicardium impressum, Morris and Lycett, ‘ . 213 
59. Fimbriella levigata, Sowb. Cretaceous; England, . 213 
