THE CAMBEIDGE GAULT AND GREENSAND. 297 



There are three species of Hinnites in the "Wbodwardian Museum: 

 two of these have been named respectively H. trilinearis and H. 

 pectinatus by Mr. Seeley ; the third is unnamed, but closely corre- 

 sponds with the figures and descriptions of H. Studeri from the 

 " Gault superieur." It appears to differ from H. trilinearis by wanting* 

 the striae on the ribs, which are also more numerous, and have 

 striated interspaces ; the flat attached valve is more finely ribbed. 



Plicatula pectinoides, Sow. 



Plicatula pectinoides, Sow. Min. Conch, pi. 409. f. 1. 

 Plicatula gurgitis, Pict. & Koux, Gres Yerts, pi. 47. f. 4. 

 PUcatula radiola, Gres Yerts, pi. 47. f. 3; D'Orb. Pal. Er. pi. 463. 

 f. 1-7. 



Plicatula inflata, Min. Conch, pi. 409. f. 2. 



There can be no doubt, I think, that MM. Pictet and Campiche 

 are right in considering P. gurgitis and P. pectinoides to be the 

 same species. Mr. Etheridge is also inclined to think that P. radiola 

 is only another form of the same. The variety, P. inflata, is a 

 Chalk-marl form ; and the few specimens I have seen among the 

 Cambridge nodules have all been in soft light- coloured phosphate. 

 The true P. pectinoides is characteristic of the Gault, and very 

 common at Cambridge in the state of a dark pHosphate cast covered 

 by the more or less waterworn shell. 



Spondylus gibbosus, D'Orb. 



Spondylus gihbosus, D'Orb. Pal. Er. iii. p. 658, pi. .452. f, 1-6. 

 Spondylus Brunneri, Pict. & Roux (pars), p. 516, pi. 42. f. 2. 



This species is not acknowledged in the "W oodwardian Museum ; 

 but Mr. Seeley speaks of its occurrence at Cambridge, in the Ann. & 

 Mag. Nat. Hist. 1866, vol. xvii. p. 177 ; and there can be no doubt that 

 most of those which have passed under the name of 8. truncatus belong 

 really to this last Gault form. It is characterized by the gibbose 

 shape of the umbones and general irregularity of the shell. There 

 are some iSpondyli, however, which belong to the Chalk-marl itself; 

 and their attached lower valves are common on the casts, nodules, 

 and boulders in the bed ; these may be 8. truncatus, but more pro- 

 bably 8. striatus. 



? Spondylus Dutempleanus, D'Orb. 



? Spondylus Dutempleanus, D'Orb. Pal. Er. iii. p. 672, pi. 460. 

 f. 6-11. 



There is another species of Spondylus at Cambridge with slightly 

 spiny valves, which Mr. Seeley has named S. hystrix, though there 

 is one specimen which he has marked 8. Dutempleanus. If distinct 

 from 8. gihbosus, I should be inclined to refer them all to the latter 

 species; several of them closely resemble M. d'Orbigny's figures, 

 while 8. hystrix is a much larger and more regular shell. Neither 



