8a 



Dr. Tb. Moitensen on some Echinothurids 



wanting in this species is in accordance therewith. A more 

 advanced stage is shown by A. teftseUatum, whereas the 

 exquisite form of tetradactylous }5edicellariae found in A.fenes- 

 iratum and coriaceum assigns to these species the highest 

 place in tliis series of species. The " tetradactylous " pedi- 

 cellaria? ot Hapalosoma show this genus to be derived from a 

 form with three-valved " tetradactylous " pedicellaria?, like 

 A. Oicsteni. The relations of these forms may be graphi- 

 cally shown thus : — 



A.fenestratum. 



A. coriaceum. 



Hapalosoma pellucidum. 



A. Owsteni. 



Be Meijere (' Siboga' Echinoidea, p. 36) finds in two of 

 his specimens of A. tessellatum the small form of tridentate 

 pedicellaiiai identical "with those found by me ('Ingolf* 

 Echinoidea, p. 52, pi. xiv. fi<r. 20) in the specimen from 

 'Challenger' St. 219 referred by Agassiz to Caheria 

 Q' Abthiiivsov^a") gracilis; in the other specimens they are 

 like those of the type specimen (' Ingulf Ech. pi. xiv. 

 fig. 15) : " Es fragt sich da ob dasselbe niclit mit dern 

 erwahnfen Excmidar der St. 219 identisch wUre^'j he 

 suggests that this s})( cimen is only a badly preserved specimen 

 of A. tcf-seUolHin. Through the kindness of Professor F. 

 Jeffrey Bell the specimen in question was sent to Copen- 

 hagen, so that I have been able to examine it closely, and 

 can give figures of it (PI. IV. figs. 3, 4). It is a young 

 E].ecimen (30 mm. diameter), without genital opening.-^, not 

 very badly preserved, the structure of the test being even 

 excellently seen ; but of pedicellaria? no more can be found 

 than what I have already made known in my 'Iiigoif^ work; 

 the spines are all broken. The r.ctinal side is like the inner 

 part of the actinal side of the type specimen of A. tes'teUatum^ 

 as figured in 'Challenger' Ech. (pi. xix.a. fig. 1), with a 

 primary tubercle at the outer end of each interambulacral 



