124 BRITISH CARBONIFEROUS BRACHIOPODA. 



varietal designations only, those few forms whose connection with the typical shape could 

 not be entirely established ; and by so doing I hope to concur with the views of those 

 palaeontologists who are not disposed to go so far as I feel inclined to do. No 

 trouble has been spared in the selection and illustration of the most important and 

 characteristic forms assumed by the species and its varieties, and many more intermediate 

 shapes could have been figured, had space permitted. 



Streptorhynchus crenistria, Phillips, sp. PI. XXVI, fig. 1, PI. XXVII, figs. 1 — 5 

 and 10 ? PI. XXX, figs. 14—16. 



Spirifer crenistria, Phillips. Geol. of Yorkshire, vol. ii, pi. ix, fig. 6, 1836. 



— senilis. lb., fig. 5. 

 Leptiena anomala, J. de C. Sow. Min. Con., tab. dcxv, figs. 1' (but not \ a > d > c ), 



1840. 

 Orthis umbraculum, var., Portlock. Report on the Geology of the County of London- 

 derry, Tyrone, and Fermanagh, pi. xxxvii, fig. 

 5, 1843. 



— — De Koninck. Animaux Fossiles du Terrain Carbonifere de la 



Belgique, p. 222, pi. xiii, figs. 4—7, 1843. 



— qladrata? M'Coy. Synopsis of the Characters of the Carb. Fossils of 



Ireland, pi. xx, fig. 18, 1844. 



— Bechei. lb., pi. xxii, fig. 3. 



— comata. lb., pi. xxii, fig. 5. 



— caduca. lb., pi. xxii, fig. 6. 



Leptcena Sharpei, Morris. Catalogue, p. 138, 1854. 



Strophalosia striata, Morris. Catalogue, p. 155, 1854, (part). Min. Con., tab. 



dcxv, fig. 1" only. 

 Leptcena crenistria and L. senilis, M'Coy. British Palseozoic Fossils, pp. 450 and 



452, 1855. 

 Orthis Keokuk, Hall. Iowa Report, pi. xix, fig. 5, 1858. 



— roeusta. lb., pi. xxviii, fig. 5. 



Streptorhynchus crenistria, Bav. Mon. of Scottish Carb. Brach., p. 32, pi. i, 



figs. 16—22, 1860. 



Spec. Char. — Very variable in shape, transversely or longitudially semicircular ; hinge- 

 line straight, slightly exceeding or somewhat shorter than the greatest width of the shell ; 

 cardinal angles rounded or prolonged with acute terminations ; ventral area variable in 

 width, flat, and divided by a fissure covered with a pseudo-deltidium ; dorsal area linear. 

 Ventral valve variable in its curves, slightly convex at the beak, flat in the middle, and 

 partly concave near and at the margin, or more or less regularly convex throughout ; beak 

 straight, produced, and often twisted or irregularly inclined to one side. Dorsal 

 valve moderately or extremely convex. Surface of both valves covered with numerous 



