140 SVEN LOVEN, ON THE ECHINOIDEA DESCRIBED BY LINN^US. 



laterales majusculae sex 1. septem, utrinque in granula abientes 

 sensim demiuuta, per series haud ita distinctas transversas dis- 

 posita, confertissima, in sutura media minima. 



(A)LOR griseo-fuscescens ambulacris et calyce saturatioribus. 



Men.suk.e: diameter 84 mm.; altitudo Go mm. 



The specimen, of a size bnt rarely seen in collections, is 

 evidently fullgroAvn, and the specimens witli wliioli it will 

 liave to be compared may be expected to be younger and to 

 present difFerenecs dej^ending on different degrees of indivi- 

 (Uial developmeut. 



The growth of the test of all Echinoids, it is well known, 

 is eftected by the addition of new plates at the aboral margin 

 of ambulacra and interradia, combined with the gradual ex- 

 pansion of those already formed, tlieir breadth increasing at 

 a greater råte than the hcight. In the Cidaridae the develop- 

 mcnt of the primary verrucae is simultaneoas with that of 

 new plates, every one of these in the act of forming bearing 

 already a primary tubercle with its scrobicule still unexpanded 

 hut distinct. Thns there are in all ages as many verrucae 

 as there are plates in the vertical series, and consequently a 

 less nnmber of jirimary verrucae in the interradial series de- 

 notes the younger specimens. Similarly, it may be expected 

 that the middle areas, ambulacral and interradial, when found 

 open and broad in the matare specimen, will be seen to be 

 narrower in the youug, or even closed, from the scrobicular rings 

 of the two series bcing still approximated or even conti- 

 guous. 



When specimens of the Cidaris papillata Leske of various 

 sizes are compared, they are found to present certain conspi- 

 cuous differences consistent with these relations of the grow- 

 ing parts. A specimen of 24 mm. has the two marginal series 

 of ambidacral primaries closely coutiguous above and below, 

 and it is only near the ambitus that they are slightly sepa- 

 rating so as to give room, on each plate, for one single se- 

 condary verrucula just about to form between them, alternately, 

 close to the suture. In specimens of 41 and 46 mm. these 

 first secondary verrucula^ are linished and free, and can be 

 followed to near the peristome, but not equally near to the 

 top. At the size of 54 mm. a second series of secondaries 



') Al. Aoassiz, Revision, Pl. I, /, fig. 2. 



