L78 CRETACEOUS LAMELLIBRANCHTA. 



1854. Mactba angulata, .7. Morris. Cat. Brit. Foss., ed. 2, p. 209. 



1865. F. J. Pictet and G. Campiche. Foss. Terr. Cret. Ste. 



Croix (Mater. Pal. 



Suisse, ser. 4), p. 129. 

 1870. F. Stoliczka. Palaeont. Indica, Cret. Fauna S. India, 



vol. iii, pp. 55, 56. 



Non 1851. J. Miiller. Petref. der Aachen. Kreidef., pt. 2, p. GG 



(= M. Bosquetiana, Stoliczka). 

 1901. F. Sturm. Jahrb. d. k. preuss. geol. Landesanst. fur. 



1900, vol. xxi, p. 84, pi. viii, fig. 1. 



Description. — Shell small, convex, subtriangular, slightly inequilateral, with 

 the antero- and postero-dorsal parts bending rapidly to the margins. Antero- 

 dorsal margin long. Anterior margin rounded. Ventral margin convex, forming 

 an angle with the posterior margin, which is truncated, oblique, and slightly convex. 

 Umbones prominent, pointed, curved inwards, with a carina which extends in a 

 gentle curve to the postero-ventral angle. Ornamentation consists of fine con- 

 centric ribs, which become fewer and stronger near the antero-dorsal and postero- 

 dorsal margin. 



Measurements : 



(1) (2) (3) (4) 



Length 14 . 13 . 10 . 8 mm. 



Height 12 . 10-5 .8 7 „ 



(1 — 4) Blackdown. 



Affinities. — In form and ornamentation M. angulata resembles M. Warrenana, 

 Meek and Hayden, 1 but the latter is of larger size and the umbones show a distinct 

 anterior curvature. 



A species found in the Aachen Greensand, now known as M. Bosquetiana, 

 Stoliczka, was identified with M. angulata by Miiller, but is distinguished from 

 the latter, as Stoliczka pointed out, by its greater length, smaller convexity, rounded 

 posterior margin, and other characters. 



Type. — From Blackdown ; in the Bristol Museum. 



Distribution. — Upper Greensand (zone of Schlcenbachia rostra to) of Blackdown 

 and Haldon. Recorded by Barrois from the Upper Greensand of Lulworth and 

 by Jukes-Browne from the equivalent of the Blackdown Beds at Sidmouth. 



1 Meek, 'Invert. Cret. and Tert, Foss. U. Missouri ' (1876), p. 208, pi. xxx, fipj. 7. Whiteaves, 

 ' Mesozoic Foss.' (G-eol. Surv. Canada), vol. i (1879), p. 142, pi. xvii, fig. i», pi. six, ii-\ 3. 



