ZOOLOGICAL CHAB WTKKs. 128 



difference between Pentremites Pailleti [PL IV. figs. 8-10] .... and Woodmani 

 [PL XIX. figs. 13-10], .... show no gi'eater divergences than there exisl between 

 .... P.Jlorealis [PL II. fig. 3] .... and oSftn waftw | PL II. fig. 4]" ! ! It is upon 

 these characters, which he neglects, that we have founded the new generic types 

 Phamoschisma, Cryptoschisma, Schizoblastus, Cryptoblastus, Mesoblastus, and Meta- 

 blastus for the reception of species which were formerly known only under the very 

 general name Pentremites. Say's name lias had to undergo the same restriction of its 

 meaning as was the case with the generic names Cyathocrinus, Actinocrinus, and 

 Poteriocrinus of Miller. A very large number of species have been described under 

 each of these names, and they have been found to fall into certain very definite 

 groups, for one of which Miller's original designation has been retained. 



The genus Pentremites began to undergo the same process when D'Orbigny 

 established Pent remit idea in 1849. In the course of the next two years Olimnitcs 

 and Slceacrintis were proposed by Troost and Roemer for the Pentremites Vemeuili of 

 1841, a species, by the way, which is nowhere mentioned by Hambach. Granato- 

 crinus, though proposed in 1850, was not formally adopted by Hall till 1SG2. 

 Orophocrinus followed in 1804, Troostocrimcs in 1805, and Tricoelocrinus in 1808. 

 Schizoblastus and Phcenoschisma were proposed by ourselves in 1SS2 ; and we shall 

 now define four more generic types for the reception of species which were first 

 referred to Pentremites, viz. Cryptoschisma, Mesoblastus, Oryptoblastus, and Meta- 

 blastus. We believe that our reasons for this course will meet with the approval of 

 scientific palaeontologists, though we do not suppose for a moment that they will 

 commend themselves to Hambach. 



At the same time we have been very much impressed by the remarkable manner 

 in which some of the different generic types are linked together. Each of the three 

 irregular genera is very well defined ; while the same may be said of Acentrotre- 

 mites, with its spiracles on the radio-deltoid suture (PL XIII. figs. 18, 19), and also 

 of Cadaster, which has no hydrospires in the anal interradius (PL XIII. figs. 1, 4). 

 It i>~ perhaps also true of Granatocrinus, with its deltoid perforated by the single 

 spiracle. But an abnormal specimen, in which the hydrospire-canals of one inter- 

 radius open separately (PL VII. fig. 13), is the first indication ot a transition towards 

 Heteroblastus (PL VI. figs. 3, 4) and thence to Cryptoblastus (PL VII. figs. 14, 15), 

 which resembles Granatocrinus in its external form and in the possession of an 

 hydrospire-plate. On the other hand, the presence of this plate distinguishes 

 Cryptoblastus from Schizoblastus, which has spiracles closely similar to those of the 

 former genus (PL III. figs. 1-3) ; and the two Irish species of Seldzoblastus further 

 resemble Cryptoblastus in the confluence of the anus with the two posterior spiracles 

 (PL VIII. fig. 9 ; PL XVI. fig. 12), a character which does not occur in the American 

 species of the genus (PL III. figs. 1-3; PL VI. fig. 10). In this latter respect, and 

 also in the absence of an hydrospire-plate, Schizoblastus Sayi approaches Elaaerinus 



