DESCRIPTIONS <>K THE 8PECIE8. 231 



in <>. Nbrwoodi (PI. VII. figs. 7 9). Bu1 herein lies the whole difference between 

 the two species. In the latter type the hydroBpire-canals at the sides of the radial 

 sinus enter the substance of the deltoids at the sutures between them and the radials, 

 the two within each deltoid converging on the spiracle at its central end. There are, 

 consequently, no hydrospire-pores aloii^ the ambulacra! edges of the deltoids, as there 

 is no canal beneath the lancet-plate into which they could lead. 



In the so-called l'i mtremitt s melo, however, there is an altogether different arrange- 

 ment (PI. VII. fig. 15). As in Granatocrinus (PI. X. fige. II. 12), there is an 

 hydrospire-plate between the lancet-plate and the walls of the radial sinus; but this 

 plate does not extend upwards above the radio-deltoid suture, so that the lancet-plate 

 comes into direct and continuous contact with the deltoids. The proximal ends of 

 these last, and also, though in a less degree, the lancet-plate itself, are notched by the 

 spiracles ; and the hydrospire-canal into which each spiracle leads is concealed 

 beneath the lancet-plate until it opens to the exterior through the hydrospire-pores 

 along the ambulacral edges of the radials. It was this character which suggested to 

 us the name Cryptoblastus, when we found it necessary to separate Pentremites melo 

 from the «;enus Schizoblastus, in which we formerly placed it. The deltoids of Schizo- 

 blastus are of variable size, as they form the greater part of the calyx in S. Rofei 

 (PI. VIII. fig. 10), while in S. melonoides and S. Bailii (PI. VI. figs. I 5, I 6 ; PI. XVI. 

 figs. 12, 13) they are as small as in Cryptoblastus melo (PI. VII. hgs. 14, 15). But 

 in both of these species there are hydrospire-pores at the sides of the deltoids, and we 

 have been unable to determine the presence of an hydrospire-plate either in these 

 two species or in S. Rofei and A', Sayi. In one American species, however, which we 

 formerly referred to Schizoblastus on account of its having divided spiracles like 

 S. Sayi, we have found essentially the same morphological characters as in Crypto- 

 blastus melo. We refer to Granatocrinus pisum, M. 6c W., specimens of which have 

 been recently received by one of us from an American correspondent ; and they show 

 the same absence of pores along the sides of the small deltoids, and the presence of 

 an hydrospire-plate between radial and lancet-plate as we have noted in Cryptoblastus 

 melo (PI. VII. fig. 15). As in this species too, the posterior spiracles are confluent 

 with the anus, which is not the case in Schizoblastus Sayi. The same is the case in 

 Eloeacrinus Kirkwoodetisis, which was described by Shumard l as being " nearly allied 

 to E. (Pentremites) melo" and as having long radials, which implies correspondingly 

 small deltoids. 



There are various other American species which have been described under Granato- 

 crinus, and have been said to be more or less like G. melo. But we do not think that 

 any of them can be referred to Cryptoblastus. Thus, for example, G. melonoides 

 (PI. VI. figs. 15, 16) appears to us to be a Schizoblastus, while G. lotoblastus, White -, 



1 Trans. St. Louis Acad. Sci. 1863, vol. ii. no. 1, p. 113. 



2 Report Wheeler's .Survey West of 100th Meridian, 1s7-j. vol. iv. p. SO. 



