SANGUINOLITES INTERRUPTUS. 383 



anterior. At the lowest point the ribs are bent upwards and somewhat backwards 

 at an acute angle ; and, passing over the oblique gibbosity of the valve, they soon 

 become obsolete, leaving the dorsal slope smooth or only finely striate. In full- 

 grown shells, towards the lower margin in front the ribs may become broken a 

 little, and their line somewhat irregular. 



Dimensions. — PI. XLII, fig. 7, measures — 



Antero-posteriorly . . . .27 mm. 



Dorso-ventrally .... 20 mm. 



From side to side (estimated) . . .10 mm. 



Locality. — England : in a band of marine shale, about 500 feet below the third 

 bed of Millstone-grit, Congleton Edge, Cheshire ; Redesdale Ironstone, Northum- 

 berland. 



Observations. — I have founded this species on three specimens, two of which 1 

 collected from the bed mentioned above at Congleton Edge, and I obtained a 

 single specimen from Redesdale. Although neither specimen is absolutely 

 perfect, the surface-markings are so peculiar that it was impossible to refer the 

 species to any of those hitherto described. 



PI. XLII, fig. 7, possesses the right valve in an almost perfect condition, 

 except that the posterior slope is crushed, and the shell appears more carina te 

 than it really is, judging from the uncrushed portion of PI. XLII, fig. 6. Tliere 

 can be no doubt of the propriety of referring this shell to the genus Sangninolites, 

 from observation of the escutcheon and the surface-sculpture. 



In front S. y-scriptus is like ;S'. interruptus, but the whole shape of the shell is 

 different, being subquadrate, while the latter species is almost elliptical, and, 

 moreover, does not possess the characteristic V-shaped bend in the ribs just 

 anterior to the oblique fold. It occurred to me that this V-bending might be due 

 to crushing ; but it is present equally in the young and uncrushed part of the 

 valve, and cannot possibly be duo to any but biological causes. 



Sangdinolites jnteuruptus, sp. nov. Plates XLII, figs. 8 — 10; XLIX, figs. 10, 



10 a. 



Specific Characters. — Shell very inequilateral, transversely elliptical, obliquely 

 gibbose, narrower from above downwards, in front than behind. The anterior end 

 is short, compressed, much narrowed by the approach of its upper and lower 

 margins, its border bluntly rounded. The inferior margin is curved, and descends 

 for its anterior two thirds with a slight sinuation at the junction of the anterior 

 and middle thirds ; it then becomes curved upwards to meet the posterior border, 

 the postero-inferior angle being bluntly rounded. The posterior border is straight. 



