254 MESSKS. G. W. LAMPLTJGH AlfD J. F. WALKEB ON [May I903, 



Dimensions : — length = 18*5 millimetres ; breadth = 15 mm. ; 

 thickness = 11 mm.; and the apical angle = 92*5°. 



This species somewhat resembles Zeilleria Juddi, "Walker, in its 

 ovoid shape, but it is a more regular ovoid globose form, and is 

 not laterally depressed, its beak is also shorter, and the beak-ridges 

 are less concave. Probably our species belongs to the subgenus 

 OrnitheUa. 



MaGAS (?) LATESTRIATA, nobis. (PI. XVII, figs. 9 rt-9 d.) 



Shell circular ; the larger valve is much more convex than the 

 smaller valve ; the greatest thickness is about the centre of the shell : 

 the lateral margins are sharp and regularly curved: front margin 

 rounded, non-plicated, and not thickened. Shell-surface slightly 

 granular, and ornamented on both valves by fine radiating striae 

 which are wide apart and reach to the beak. The larger valve has 

 its greatest thickness near the centre, and is regularly convex : 

 the striae are best developed towards the lateral margins of the 

 shell. The beak is short, nearly straight, and truncated by a large 

 circular foramen ; and it is separated from the hinge-line by a 

 deltidium in two pieces. The beak-ridges are concave ; the hinge- 

 line is slightly curved. The smaller valve is slightly convex, the 

 greatest width being about one-third of the distance from the 

 posterior margin. A dark line, extending to about one-third of 

 the shell, shows that it bad a long loop. 



Dimensions : — length = 18*5 millimetres ; breadth = 1 7'5 mm. ; 

 thickness = 9 "75 mm. ; and the apical angle = 76*5°. 



We have not been able to examine the loop of this shell, but it 

 probably belongs to the genus Mayas. In shape it somewhat 

 resembles the large rounded specimens of Zeilleria tamarinda ; but 

 it is easily recognized by the ornamentation of its shell-surface, by 

 the less proportional convexity of the smaller valve, by the beak 

 being straighter, by the beak-ridges forming a smaller area, and by 

 the absence of a fold on the front margin. 



Magas oethieormis (d'Archiac). (PI. XVII, figs. 10rt, 10 b, & 11.) 



1847. Terebratula orthiformis, d'Archiac, ' Fossiles du Tourtia ' Mem. Soc. Geol. 



France, ser. 2, vol. ii, p. 333 & pi. xxii, fig. 4. 

 1852. Mayas orthiformis. Davidson, ' Brit. Cret. Brachiop.' Monogr. Pal. Soc. 



p. 22, note. 



We have obtained several specimens which we refer to this 

 species : they appear to be plentiful at Shenley, but are difficult to 

 find, on account of their small size. D'Archiac states that the shell 

 is sufficiently characterized by its form, which recalls that of Orthis. 

 The hinge-line is nearly straight, from the extremities of which the 

 shell describes three-quarters of a circle ; the larger valve is more 

 convex than the smaller one, and has a short beak forming an 

 obtuse angle with the hinge-line ; foramen triangular ; deltidium in 

 two pieces, which do not surround the foramen. The surface of 

 the shell is covered with faint radiating striae, with transverse lines 



