JURASSIC AND TRIASSIC BRACHIOPODA. 177 



Shell small, smooth, subpentagonal, straight in front : valves nearly equally convex 

 and often thickened at the margin, without fold or sinus ; beak much incurved, and 

 truncated by a small circular foramen slightly separated from the hinge-line by a short 

 deltidium, beak-ridges sharply defined. 



Length 6, width 5^, depth 4 lines. 



Obs. — This small and well-marked species, as justly observed by Dr. Oppel, so 

 closely resembles Wald. tamarindus from the Neocomian, that it would be difficult to 

 point out in what they differ ! Although specimens of the shell from the Coral Rag of 

 Calne have been in my possession since 1853, it is only recently that the fossil was 

 recognised, by the Rev. J. E. Blake, as a British species. He found specimens agreeing 

 with those from Vils in the Coral-rag of Hilmarton, and Mr. Hudleston found it at 

 Earingdon. It has also been recently discovered by Mr. Walker in the Coral-rag of 

 Seames in Yorkshire. We have therefore now recorded from four British Coral-rag 

 localities all the specimens presenting the same shape and size. A dark line visible on 

 the surface of the smaller valve indicates that it belongs to the genus Waldheimia. 



W/VLDHEIMIA RESUPINATA, W. FLORELLA, W. MoOREI, W. BaKERI^E, W. CAR1NATA, 



W. Meriani, W. impressa, and several other closely allied and similar-shaped species or 

 varieties, with concave or semi-concave dorsal, and keeled ventral valves, form a group 

 of shells all more or less intimately related, yet to some extent specifically separable. 

 Indeed, the distinctions between some of them are so small and questionable that they 

 may possibly be only varieties ; but, as some uncertainty seems to prevail about the matter, 

 it will be best, provisionally at least, to allow them to retain the names they have 

 received from different palaeontologists, especially as several of them characterise distinct 

 geological horizons. This group is also closely allied to the Neocomian carinated 

 species. 



161. Waldheimia resupinata, Sow. Dav., Ool. Mon., p. 31, PI. IV, figs. 1 — 5. 



I have nothing to add to the description I gave of this species at p. 31 of my 

 Oolitic Monograph, beyond defining its stratigraphical position. 



W. resupinata occurs in the zones of Am. margaritatus, and Am. spinatus (top of 

 Middle Lias) at Churchdown, Gloucestershire (E. Smith), at South Petherton, and 

 elsewhere. In England it is generally met with presenting an elongated groove along the 

 middle of its dorsal valve, but in some specimens described and figured by Mr. E. 

 Deslongchamps it is as wide as long, and has a mesial depression of moderate depth 

 and angularity, and in this condition it is difficult to be distinguished from some broad 

 varieties of Wald. carinata, var. alveata, from the Inferior Oolite, as may be seen in 

 some of the figures of W. resupinata in pi. 24 of M. Deslongchamps' ' Brachiopodes 



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