522 EEV. G. F. WBTDEOEtfE ON SOME EOSSILS 



Nucula ^eqtjilateealis, Terq. & Jourd. ? 



1858. Nucula, sp., Quenst. Jura, t. 73. fig. 52. 



1871. N. cequilateralis, Terq. & Jourd. Mem, Soc. Geol. Fr. ser. 2, 

 vol. ix. t. 11. f. 23-25. 



I have collected some minute shells from the Humpliriesianus- 

 zone of Bradford Abbas, which have a close resemblance to this 

 shell, but are rather less transverse and equilateral, so that a distinct- 

 escutcheon may be observed. From the Liassic Nucula jyalmce, 

 Quenst. Handb. t. 44. fig. 8, and Jura, 1. 13. f. 42, they differ by having 

 a much smaller umbo and being a more perfect oval. As they are 

 all closed valves, I am not at all certain that they even belong to 

 this genus, in spite of their general resemblance to Terquem's shell. 



Nucula subglobosa, Romer. Plate XVIII. fig. 4. 



1836. Nucula subglobosa, Rom. Ool. Geb. t. 6. fig. 7. 



1837. N. nucleus, Deslongch amps, Mem. Linn. Soc. Norm. 1837, 1. 1. 

 fig. 8. 



1849. N. subglobosa, D'Orb., Prodr. sect. 9, no. 209. 



1849. N. nucleus, D'Orb., Prodr. sect. 10, no. 344. 



1853. N. subglobosa, Chap. & Dew., Foss. Lux. t. 24. fig. 8. 



1858. N. Hammeri, Quenst. Jura, t. 43. fig. 7, 8. 



1869. N. subglobosa, Brauns, Mittl. Jura, t. 261. 



Shell exceedingly convex, ovoid, truncated in front, rather sharply 

 convex behind. IJmbo anterior, proximate. Surface, with irre- 

 gular impressed growth-strise. Lunulse distinct. Inferior margin 

 curved. Structure massive. Hiuge large, curved, covered with 

 numerous parallel teeth. 



The closed shell measures 5 lines long by 6 wide and 4| deep. It 

 is common in the rubbly beds of the Humphriesianus-zoiiQ at Brad- 

 ford Abbas. There are also numerous examples of it in the Jermyn- 

 Street Museum from various localities. 



This species is undoubtedly the N. nucleus, Desl., from the Infe- 

 rior Oolite of Calvados, with which it has been identified by the 

 Jermyn-Street authorities ; but I am unable to see any difference be- 

 tween it and N subglobosa, Rom., or Quenstedt's rounder variety of 

 N. Hammeri. His wider variety, which agrees with Goldfuss's 

 t. 125. fig. 1, and is probably the same as jV. Hammeri, Defr., as 

 argued by Quenstedt, p. 313, against D'Orbigny, occurs rather 

 higher in the English Jurassic series. - "< 



N. subglobosa is given by Morris and Lycett as a synonym of 

 N. variabilis (Sow.), from which the present shell is certainly 

 distinct ; but while upon comparison Romer's species seems decidedly 

 separate from that figured in the monograph, it does not appear 

 distinguishable from these Dorsetshire fossils, which vary consider- 

 ably, and are often wider than the specimen figured in the accom- 

 panying plate. I therefore feel obliged to retain Romer's name in 

 preference to that of Deslongchamps. 



