GENEEA AKD GEOTJPS OF THE ECHINOIDEA. 35 



Pamily Cidaeid^. 



Section II. 



The ambulacral pairs of pores biserial. 



Q-enus Diplocidaeis, Desor, 1854-58, Synopsis, pp. 45 & 439. 

 CoUeau, 1862, Bev. et Mag. Zool. vol. xiv. p. 185, pi. 10. 



Test large, spheroidal, wider than high. 



Apical system large, solid, pentagonal, flush. 



Ambulacra narrow, straight ; poriferous zone as broad as the 

 interporiferous area ; pairs of pores very numerous, close, biserial, 

 alternating more or less, placed in low primary plates which 

 are single actinally, and which form compound plates elsewhere, 

 these being double or triple combinations of low primary plates. 

 Interporiferous area narrow, with two vertical rows of large 

 granules with mamelons and a narrow, bare median space. 



Interradia broad ; plates few, high, 7-8 ; two vertical rows of 

 large, perforate, scrobiculate, primary tubercles, which may or 

 may not be crenulated, in each area ; miliary zones large, with 

 scattered granules. 



Peristome narrow, with narrow ambulacral lips ; branchial 

 incisions absent. Jaws strong ; the foramen of the pyramid small 

 or absent. Perignathic girdle with interradial ridges only, and 

 they are notched and bilobed. 



Spines long, thick, cylindrical, granular, and pustulate in longi- 

 tudinal ridges. 



Fossil. Oolite : England ? ; Europe ; N. Africa. 



The next genus is placed here provisionally ; it has four coronal 

 interradial plates in each interradium, but not in every part of 

 the areas ; and the nature of the peristome is unknown in the 

 species. The shape and the construction of the ambulacra are 

 very remarkable ; and it must be remembered that A. Agassiz 

 found divisions in the interradial plates of Astropyga radiata 

 (' Challenger ' Echini, pi. x a. fig. 9, 1881). 



G-enus Teteacidaeis, Gotteau, 1872, Bev. et Mag. de Zool. ser. 2, 

 vol. xxiii. p. 445, pi. 29. 



Test large, circular in equatorial outline, tumid, broader than 

 high, depressed, spheroidal. 



3* 



