430 PROF. F. J. BELL ON THE ECHINOMETRIDiE. [MaV. 15, 



I am unable to give any information as to the oculars of S. mexi- 

 ca7ius or S. nucliis : no mention is made of this character iu the 

 diagnoses given in the ' Revision ;' nor are they there figured. Neither 

 species is represented in the British Museum. 



With regard to the characters of the radius, the number of species 

 on which I have any thing to report is, unfortunately, still smaller ; 

 the buccal apparatus oi S. franciscanus, S. ffibbosus, and/S. depressus 

 being wanting from the British-Museum specimens. 



S. tuberculatus would appear to be distinguished by the fact that 

 the radius is not notched terminally, while in albus, armiger, erxj- 

 throgrammus, intermedins, and purjmratus it is always so notched ; 

 S. bullatus rather has the free end of the radius deeply grooved than 

 notched. 



Characters of ascending and descending Tooth-processes. 



(a) Both present . . . . i. erythrogrammus. 



{ft) Ascending process evanescent ii. armiger. 



(y) Ascending process absent iii. albus. 



iv. bullatus. 

 v. drobachiensis. 

 vi. interniedius. 

 vii. lividus. 

 viii. purpuratus. 

 ix. tuberculatus. 



Sph^irechintjs. 



The difficulties which are offered by the great development of the 

 tubercles and the special characters of the gill-cuts iu species of this 



Fig. 2. 



Eadius of S. granular is, seen from in front. 



genus have always appeared to me to stand in the way of the view 

 taken by Prof. A. Agassiz, which regards this genus as a subgenus of 

 Strongylocentrotus. An examination of the buccal apparatus seems to 

 me to do more than justify this hesitation. The free end of the radius, 

 in place of being merely widened out at its end, presents a strong 

 and deep furcation, each leg of the fork measuring 6 millim., in a 

 radius of which the azgyos piece was 1 1 millim. loug, and the angle 

 so wide as to separate the free ends of the legs by 5 millim. It 

 has not been my fortune to meet with so aberrant an arrangement iu 

 any other regular Echiuid save Toxopneustes. 



