JURASSIC AND TRIASSIC BRACHIOPODA. 163 



a gentle convex upward curve. Beak rather narrow, incurved, carinated, and truncated 

 by a small circular foramen, separated from the hinge-line by a deltidium in two pieces ; 

 beak-ridges very sharply defined. Surface of valves smooth, and marked only by 

 fine concentric lines of growth. Proportions variable ; a large example (the type) 

 measuring — > 



Length 1 inch 11 lines, width 1 inch 5 lines, depth 11 lines. 



In 1851, when I proposed the name sub-numismalis for this species, I had seen but 

 one specimen, and felt uncertain with respect to its distinguishing features. Since then 

 several well-preserved and characteristic examples from the Marlstone or Middle Lias, of 

 Chideock, near Charmouth, in the Museum of the School of Mines (Day Collection), as 

 well as others collected in the same locality by Mr. J. F. Walker, in addition to the fine 

 series of French examples figured by Professor E. Deslongchamps in the work above 

 referred to, have convinced me that the shell deserves a specific designation. It varies 

 considerably in shape. When quite young, and up to a certain age, it is almost circular, 

 and but slightly elongated, but becomes more so with age ; it is then longer than wide 

 and longitudinally oval, by which character, in addition to the absence of a defined 

 depression in either valve, and a nearly straight front, it may be easily distinguished 

 from W. numismalis, W. cor, W. quadrijida, W. cornuta, and other allied forms. Some 

 specimens are more convex than others. It was found by the Rev. F. Smithe in the 

 Middle Lias (Zone of Am. margaritatus at Churchdown, Gloucestershire, Sup., PI. 

 XXI, fig. 4). It also occurs in the Marlstone at South Petherton, Somerset, where it 

 is rare. 



In France it is, according to Mr. E. Deslongchamps, a common fossil at May, 

 Fontaine-Etoupe-Four, Bretteville-sur-Laize, and other places in Normandy. 



143. Waldheimia Darwini, E. Desl. Sup., PI. XXIV, figs. 9, 10, 11. 



Tebebratula (Waldhemia) Darwini, E. Desl. Brackiopodes Jurassiques, p. 128, 



pi. xxx, figs. 1—10, 1863. 



Shell small, much compressed, either as wide as long and truncated in front, or 

 longitudinally oval and rounded in front. Valves not very convex, that of smaller valve 

 often depressed or flattened along the middle. No fold nor sinus ; beak incurved 

 and perforated by a small circular foramen, slightly separated from the hinge-line by 

 a narrow deltidium, beak-ridges sharply defined. Surface smooth. Dimensions of two 

 specimens : 



Length 7, width 7, depth 4 lines. 

 j> o, j, o, ,, o ,, 



