KCHINOIDEA. II. 8l 



disconnected like that of P. lagioiciila. It is be\-ond doubt that in a restriction of the genus the name 

 Poiirtalcsia has to be retained for the group of species to which P. luiranda beloiigs. Thus far I agree 

 with Agassiz, whose above cited proposition of a subdivision of the genus is evidently mucli more 

 in accordance witli tlie natural relations of the species than Duncan's and Poniel's subdivisions. 

 Nevertheless I cannot fuUy accept Agassiz' subdivisions either. 



On reviewing the characters of the .species it seenis to me that one feature mav reasonably be 

 taken to be of primar\- importance for a grouping of the species, viz. whether the bivial ambulacra are 

 interrupted b)- the postero-lateral interambulacra or not. Also the shape of the test seems rather im- 

 portant, whereas pedicellariæ and spines seem to be of secondary importance. The character of the 

 apical system, whether it is disconnected or compact, cannot be nsed, all the species thus far known 

 having in faet a disconnected apical system '. 



The bivial ambulacra are continuous in cariinita (almost certain!), phialc. paradoxa and pro- 

 bably cfrnfopyga. disconnected in the other species [P. rosea. hispida and mircuida are unknown in this 

 respect, but the two latter ma\' well be supposed to have them disconnected). Further it is to be re- 

 marked that P. cari)iata differs from all the other species in having two pores and tube-feet in the 

 ambulacral piates I. a. i and V. b. i. [P. rosea and ntinutda again are unknown in this respect, though 

 the latter may doubtless be supposed to have the pores single as in lagiincula etc). Finally it may 

 perhaps be a character of some importance whether the dorsal piates of the odd posterior interambu- 

 lacrum are paired or alternating, the latter being, of course the more primitive structure; they are 

 alternating in /-■. carinata and ccratopyga. paired in Jcffrcysi. Waiidcli. hispida , lagiiiiciila. Taiiiieri. 

 phiale and paradoxa. Upon the whole this character evidently cannot, however, be taken too rigorously, 

 the paired piates generally showing more or less distinct traces of then- originally alternating condition. 

 In typical examples the difference between these structures is verv conspicuous, as seen e. g. by a 

 comparison of Fig.s. 51 and 52. PL VII in Lovén's: On Pourtalesia. In accordance with the characters 

 pointed out here as the more important, I think the following grouping of the species will prove to 

 be the natural one: 



1. Bivial ambulacra continuous; two pores in the ambulacral piates I. a. i and 

 V. b. I. Test not especially widened or elongate. Dorsal piates of odd 

 interambulacrum alternating P. carinata. 



2. Bivial ambulacra continuous; one pore in the piates La. i and V. b. i. Test 



very elongate ; dorsal piates of odd interambulacrum paired P. phialc and paradoxa. 



3. Bivial ambulacra (probably) continuous; one pore (sometimes two) in tlie 

 piates I. a. i and V. b. i. Dorsal piates of odd interambulacrum alternating. 



Test much widened anteriorl)- P. ccratopyga. 



4. Bivial ambulacra disconnected; one pore in the piates I. a. i and V. b. i. 

 Dorsal piates of odd interambulacrum paired. Test not especially widened 



or elongated P. laojdiciila, miranda (?), 



Unknown : P. rosca. Taniicri, Jcffrcysi. Wandcli and hispida. 



I Whether the genital piates be separate or not, seenis to be a character of small importance, since both cases may 

 occur in the same species. Likewise the presence or absence of the labrum is of small importance, as shown by its great 

 variation in P, Jeffreysi and Waiideli. 



The Ingolf-Expeiiition. IV. j. jj 



