OF WESTERN SIND. 263 



Illustrations of the large Specimen with anterior truncation in Plate XLI. 

 Fig. 3. The actinal surface : natural size. 



4. The peristome of another specimen : natural size. 



5. Outline diagram of the peristome. 



6. EcHiNOLAMPAS DiscoiDEUS, d'ArcMac, var. j3, Duncan & Sladen. 



This variety of the species is small and flat, and in one the length is 50 millim. 

 breadth 53 millim., and height 19 millim. Eelative length to breadth 1 : 0-98, and 

 length to height 1 : 0-32. 



The next variety, also a flat one, is thus described by us : — 



7. EcHiNOLAMPAS DISCOIDEUS, d'Archiac, var. y, Duncan & Sladen*. 



The test is depressed, ovoid, broadest on the posterior half; it is longer than 

 broad in a slight degree, and much broader than high. The relational proportions are : 

 length 1, breadth 0-9, height 0-38. 



The highest point is central, and behind the excentric in front apical system- 

 The test slopes rather flatly, but with a gentle curve to the front, and much more 

 boldly, _and with some tumidity, posteriorly. The margin is nowhere tumid, but more 

 swollen and rounded posteriorly than anteriorly. Actinally the peristome is central 

 and sunken, the test being slightly tumid between it and the margins ; there is some 

 convexity between the- peristome and the inframarginal, elliptical periproct, which is 

 close to the posterior edge. The fore part of the actinal surface dips down slightly, 

 and the test rests on a surface close to the anterior margin, and elsewhere between the 

 peristome and the margin. 



The excentric in front apical system is small and with rather large generative 

 pores ; the anterior are the closest, and aU are oblique. 



The odd ambulacrum is, as are the others, flush with the test, the poriferous 

 zones being barely sunken. The interporiferous area is lanceolate, widely open at the 

 end ; and the poriferous zones, narrow and long, show no tendency to close ; they are 

 of the same length, and are slightly narrower at their termination. This ambulacrum 

 is as long as the longest poriferous zone of the antero-lateral ambulacra, and 

 only a little shorter than the postero-lateral ambulacra. The breadth of the odd 

 ambulacrum, like that of the others, is not great, but it equals that of the posterior, 

 although it is very slightly less than that of the antero-lateral pair. 



The antero-lateral ambulacra, nearly transverse, are widely open, and the posterior 

 poriferous zone is more bent than the anterior. They extend close to the margin. 

 The postero-lateral ambulacra are slightly sinuous, long and open ; the anterior zone is 

 the longest. The poriferous zones generally are narrow, 1\ times less than the 

 interporiferous areas. The ornamentation of the interporiferous areas is slightly 

 smaller than that of the interradia; it is not crowded in these last. The actinal 

 ornamentation is larger than the abactinal, and is very large in the posterior inter-radium. 

 The anterior bourrelets are well developed. 



* We retain the specific name given by MM. d'Archiac and Haime without modification. 



2n 



