1865.] 



DTTKCAN — ASIATIC ECHINODERMATA. 



355 



Chalk in the form of a variety which is subconical and not so much 

 depressed as the type, and that both have five generative pores. 



The small tubercles, which are crenulated and perforated, the 

 position of the anus, and the general form of the test are repeated 

 sufficiently to admit the following under one species. The series will 

 then stand thus : — Holectypus Cenomanensis, Gueranger. Varieties : 

 1. some French unnamed forms, which vary very slightly from the 

 type ; 2. var. 1, from South-eastern Arabia ; 3. var. 2, from South- 

 eastern Arabia ; 4. var. Turonensis, from the Lower and Upper Chalk ; 

 5. Yav.planatus, from Texas. The species follows the law, that those 

 widely dispersed vary greatly ; and its great diffusion, both in area 

 and in depth, is very remarkable. 



II. CiDAUis CENOMANENSIS, Cottcau. The variety of this species 

 differs from the type in having the second or internal two rows of 

 grannies in the ambulacral spaces barely developed. The primary 

 or external rows are like those of the type, and extend to the summit, 

 occupying the interporiferous zone for some distance. This difference 

 is insufficient to be specific ; but its recognition as pertaining to a 

 variety throws some doubt on the propriety of separating C. Ceno- 

 manensis from 0. vesiculosa, these species differing only in the granu- 

 lation of their ambulacral spaces. 



III. Hemiasteb similis, D'Orb. There is a variety of this species 

 in South-eastern Arabia, and a second at Bagh. Both have wider 

 spaces between the rows of pores in the ambulacra than the type, 

 and the test is generally more globular than in the European speci- 

 mens ; moreover the posterior ambulacral areas are a little longer 

 than in the type, but stiU they are very short. The Bagh variety is 

 broader and more globular than the South-eastern Arabian. 



Figs. 2-4. — Illustrating the structure of Cottaldia Carteri. 



Fisj. 2. 



Fiff. 4 



Fig. 2. 

 3. 



Cottaldia Carteri: side view, natural size. 

 The same : diagram of the apical disk. 



4. The rame : diagram of an ambulacral space, poriferous rones, &c. 



