1880.] PROF. F. J. BELL ON THE TEMNOPLEURIDjE. 423 



fine it in detail, but will say merely of it that it includes those forms 

 which, with a varying arrangement of their ambulacral pores, are 

 provided with more or less distinct sutural pores or pits at the angles 

 of the coronal plates. 



There is, perhaps, no group in which variations during growth are 

 more remarkable than they are in this ; there is certainly none in 

 which they are more instructive. Following the method I have 

 already adopted', I have, in the tables of measurement which form 

 the great body of this paper, expressed the absolute diameter of the 

 tests in millimetres, while for the height, the abactinal system, the 

 anal area, and the actinostome, the percentage values have been cal- 

 culated ; the poriferous zone is also occasionally added. Two re- 

 commendations present themselves for undertaking this exceedingly 

 laborious task : the changes which occur during growth are at once 

 seen ; and, secondly, an aid is afforded to that not small group of 

 naturalists who have not under their hands so large a series of forms 

 as is fortunately to be found in our own national collection. Dif- 

 ferences in proportion will not now form the chief ground on which 

 new species are established ; and the value of the British-Museum 

 series will be hereby extended to those naturalists who, for want of 

 such, are, naturally enough, led to regard their single immature 

 specimen as the representative of a new species'". 



I. Temnopleurus, Agassiz. 



The type of this genus is T. toreumaticus (see Agassiz, Introd. 

 to Valentin's Anat. du genre Echinus, p. vii, & Observations sur les 

 progres recens etc., 1841, p. 7). 



Prof. Alex. Agassiz recognizes in the genus three species, the 

 forms T. reevesii and T. gramdosus of Gray being regarded as 

 synonymous with T. reynaudi, Agass. I have carefully examined 

 Dr. Gray's types, and have been led to the conclusion that the two 

 are not representatives of the same species. 



The name Toreumaticd^ is ordinarily regarded as a synonym of 

 Temnopleurus ; but it seems that Dr. Gray nowhere defined it, and 

 it might well be allowed to fall out. 



. 1 P. Z. S. 1879, p. 662. 



^ It appears to me to be unnecessary to justify the selection, as a standard of 

 the diameter of the test, of the regular Eehinida. Save where abnormalities, easily- 

 enough detected, come to development, it seems plain that it stands in very much 

 the same relation as the diameter of the human thorax does in measurements of 

 this character, and is the nearest approach to that relation between the dimensions 

 of the head and of the thorax which has been found so useful in the case of pro- 

 portional measurements of the human subject {cf. Liharzik, 'Das Gesetz des 

 Wachsthums u. der Bau des Menschen,' Wien, 1862, p. 33). 



3 See P. Z. S. 1855, p. 39. 



