124 CATALOGUE OF THE BLASTOIDEA. 



prise all those species in which the horizontal portion of the deltoid piece is very 

 narrow, the sinus to both sides in the deltoid and lancet pieces comparatively large, 

 and so surrounded by the zigzag plicated integument that two of the so-formed 

 openings appear externally only as one." In this division Hambach places all the 

 typical Fentremites with broad ambulacra, such as P. Godoni, P. sulcatus, and 

 P. piriformis, and likewise two species of the Troostoblastidse, viz. Troostocrinus 

 Pcinwardti and Metdblastus Wbrtheni. One of its essential characters is the 

 appearance externally of only five spiracular openings, as in the Pentremites sulcatus 

 and P. elongatus, figured on PL I. figs. 4 and 10. But our other specimen of 

 P. elongatus, which has divided spiracles (PL I. fig. 5), would have to be placed in 

 Ilambach's second division along with Pentremites Burlingtonensis, which appears to 

 us to be little more than a variety of P. Godoni, as seen on PL I. fig. 2. 



The spiracles of Troostocrinus Reinwardti are also imperfectly divided (Fig. VII. A 

 on p. 112), while those of Metablastus lineatus, which Hambach admits to be an allied 

 species, are very distinctly double, as seen in PI. III. tigs. 14, 15. Both these species 

 would more properly find a place in Hambach's second division, in which the spiracular 

 openings " have to remain separate, or, in other words, where we have ten distinctly 

 visible openings." Besides Pentremites Burlingtonensis he places here the types 

 which we distinguish as Cryjjtoblastits melo, Schizoblastus Sayi, and Mcsoblastus 

 crenulatus. We regard the last named as belonging to the Pentremitida;, and place 

 the two former genera in the same family as Elceacrinus, viz. the Nuclcoblastidce. 

 Hambach appears to admit the morphological value of the generic type which is now 

 usually known as Granatocriuus ; but lie sees " no good reason to separate the first 

 division from the second because the number and relative position of these plates to 

 each other remains the same." The plates to which he refers are the deltoids, 

 which he describes as the principal cause of the differences in the spiracle-openings. 

 As, however, the number and relative position of the deltoids to each other are the 

 same in all Blastoids, and have absolutely nothing to do with the formation of 

 the spiracles, we cannot see how they affect the question of the generic position of 

 Pentremites and Schizoblastus. 



Having laid down the general principle (from which we entirely dissent) that all 

 described " Pentremites can easily be distributed in either one or the other of these 

 three divisions," Hambach x proceeds to infer that "it is therefore impracticable to 

 divide the genus Pentremites into four or five new genera." He devotes considerable 

 space to explaining how certain species differ from others " mainly in the different 

 length of the base and fork pieces," or " only in the different development of the 

 calyx pieces." We quite agree with him that these characters, as he describes them, 

 are altogether of minor importance. But they have another aspect altogether, 

 which hi' lias entirely overlooked, as will be evident from the fact that he says, "The 

 1 Trans. St. Louis Acad. Sci. 1884, vol. iv. no. Ji, p. 546. 



