384 CIDARIS. 



C1DARIDAE. 



Family Cidaridae Mil. leu, Ban d. Echinod., 18j4. (emend.) 



GONIOCIDARIDAE. 



Subfamily Goniocidarida Haeckel, Entwickel. Gesch., I860. 



Althougli the Cidaridae proper had been separated as a group from the 

 Echinidae and Salenidae by Agassi/, and Desor, yet Muller was the first 

 to analyze more in detail their structure, and to separate the family 

 Cidaridae from the Echinidae Be showed, in addition to the large number 

 of small plates composing the ambulacra! area, composed of single pairs 

 of pores arranged in a narrow vertical zone (except in a single fossil 

 genus, Diplocidaris), the great width of the interambnlacral region, the 

 small number of the coronal plates of the interamhulacral region, each 

 surmounted with biri a single primary perforate tubercle, surrounded by 

 a large scrobicular circle more or less prominent, that the poriferous zone 

 extended to the buccal edge of the imbricated buccal membrane; that the 

 actinal cuts were not in the coronal plates, hut near the actinostome in the 

 edge of tin' buccal membrane. The actinal and abactinal system are both 

 huge and of nearly the same size. The primary interambnlacral spines are 

 large, while those of the ambulacral system and of the miliary zone are small 

 flattened papillae, and never ornamented ; the papillae extend over the 

 buccal membrane. The jaws are less complicated than in the Echinidae 

 ami Diadematidae. The teeth are in shape of a gauge, like those of the 

 Diadematidae ; and the auricles, made up of independent arches, take their 

 origin from the interambnlacral instead of the ambulacral spaces. The jaws 

 have not the large triangular foramen of the Echinidae. nor are the sides 

 of the jaws connected over their central part. 



CIDARIS. 



Cidaris Klein, 1784, Nat. Disp. Echin. (See Part II., p. 252.) 



The structure of the spines is different from that of the other Echinidae. 

 A section shows the shaft to be made up of irregularly arranged small lime- 

 stone cells, closely packed, surrounded by an outer sheath of limestone 

 network, which forms the ornamentation of the spines and grows indepen- 

 dently of the inner structure. 



