294 R. M. Brijdone—New Chalk Pohjzoa. 



II. XoTES ON NKW OR IMPERFKCTLY KNOWN ChALK PoLTZOA. 



By E. M. Brydone, F.G.S. 



{Continued from tlie April Number, p. 147.) 



(PLATES XIV AND XV.) 



Semieschara Proteus, sp. nov. (PI. XIV, Figs. 1-8.) 



Zoaritim always encrusting, Avitli a very strong tendency to linear 

 and in*particular transversely linear arrangement, the gi'eat regularity 

 of occurrence and the smallness of the avicularia being unsuited to 

 the quincuncial arrangement usual among the Escharida?. 



Zooecia. If I am right in the extent I assign to this species the 

 range of vsiriation is abnormally wide. The tj'pical form of zooecium 

 is that met with in the zone of M. cor-testudinarium, and exemplified 

 by rigs. 2-5 ; here the zooecia are notably long and naiTOw, '5 mm. 

 long by "28 mm. wide being average dimensions ; the aperture is small, 

 terminal, and semicircular, but with its sides slightly straightened 

 and its top slightly flattened, and its lower lip is usually gently 

 convex, but also varies between strongly convex and practically 

 straight; the front wall is nearly but not quite flush with the side 

 walls at the foot of the zooecium, but sinks steadily towards the 

 aperture, and its surface often gives a suggestion of roughness. In 

 the zone of M. cor-angumum (Figs. 6 and 7) the zooecia are of the 

 same general type, but are wider in proportion, with averajje 

 dimensions of '52 mm. in length and -35 mm. in width ; the front 

 wall not only rises flush with the side walls at the foot of the 

 zooecium but often swells up above them, while it sinks to a greater 

 depth at the aperture and is smooth almost to sleekness ; the lower 

 lip of the aperture still varies between strongly convex and practically 

 straight, but the average convexity is less than in the preceding zone. 

 In the very rare form from the zone of H. planus illustrated by 

 Fig. 1 the zooecia are of quite different shape, -55 mm. long by 

 •4-"45 mm. wide being average dimensions ; the front wall is well 

 below the side walls at the foot of the zooecium and sinks but little 

 towards the aperture, and its surface is strongly roughened ; the 

 aperture is large anfi its lower lip projects veiy prominently, leaving 

 a deep, wide, blunt-ended sinus on either side of it. In the upper 

 part of the zone of A. quadratus there occurs quite rarely the form 

 illustrated by Fig. 8 ; here the zooecia have very similar dimensions 

 to the planus form and also its rough front wall, but the front wall 

 rises above the side walls at the foot of the zooecium, though even 

 so it is still below the end wall of the preceding zooecium, and it 

 sinks moderately towards the aperture, which is large and has its 

 sides distinctly straightened by what appears to be a definite infold 

 of the side wall, and a lower lip, which is either practically straight 

 or only slightly convex ; in this form alone is there any tendency to 

 separate side walls for adjoining zooecia. 



Ooecia small depressions in the foot of the succeeding zooecia, but 

 embraced by the end wall and covered in with an inconspicuous 

 narrowly heel-shaped root' with a concave free edge ; they occur 

 frequently, but are generally only evidenced by the bulged end wall 



