46 CATALOGUE OF THE BLASTOIDEA. 



Thanks to the kindness of Mr. Wachsmuth we are now in a position to under- 

 stand the nature of the circular duct which Mr. Hambach has obtained entire in 

 Pentremites Norwood/. We have three specimens which show portions of it and of 

 its radial extensions (PL VI. fig. 19), and we are satisfied that the latter represent 

 the canals within the lancet-pieces, as we shall explain subsequently. According to 

 Hambach, however, this circular duct unites the radial vessels beneath the lancet- 

 pieces which he thinks he has seen in the typical Pentremites. But it is by no means 

 clear that he has seen these " sublancet " vessels in Granatocrinus Norwoodi ; and we 

 are inclined to think, as we have pointed out before 1 , that he has seen his so-called 

 " longitudinal duct " in a typical Pentremites, and the circular duct in P. Norwood!, 

 which is the typical Granatocrinus. But why does he consider this circular duct as 

 uniting a series of longitudinal ducts beneath the lancet-pieces, rather than as the 

 oral ring for the system of canals which he correctly describes within the lancet- 

 pieces themselves"? 



These are relatively large canals, and were first discovered by Kofe 2 , who, however, 

 misinterpreted their nature : they were figured by Wachsmuth and Springer 3 in 

 Granatocrinus Norwoodi, and are shown in our PL XVII. in Granatocrinus (figs. 4-8), 

 Mesohlastus (figs. 9, 10), Orophocrinus (figs. 12, 13), and in Eleutherocrinus (PL XIX. 

 figs. 2, 3). We are inclined to think therefore that Hambach is right in stating 

 that the lancet-piece of Pentremites is perforated by a canal. For we seem to have 

 evidence of such a canal in our sections of the ambulacra of Pentremites piriformis, 

 P. elongatus, and P. conoideus (PI. XVIII. figs. 3, 4, G). When the summit is 

 rubbed down, it is then evident, as stated by Hambach 4 , that " these canals are 

 only the radiating rays of a pentagonal ring surrounding the central orifice." 

 According to his descriptions, therefore, there are two rings round the central orifice, 

 one which he and we ourselves have seen in Pentremites uniting the canals 

 within the lancet-pieces, and one uniting the sublancet-canals, which Hambach has 

 obtained entire from a well-preserved specimen of Granatocrinus Norwoodi. We 

 believe, however, that this is the same ring as appears in rubbed specimens of 

 Pentremites uniting the lancet-canals (PI. XII. figs. 15, 17). Its relation to these 

 canals in Granatocrinus Nonvoodi is very evident in our specimens (PL VI. fig. 

 19) ; and Hambach offers no proof whatever of the existence of a second ring in this 

 species, nor of any longitudinal duct beneath the lancet-piece, such as he describes 

 in Pentremites. 



It is just possible that the under lancet-plate with a tubular passage running 

 through it which is shown by Wachsmuth and Springer"' in their section of Pen- 



l Ann. & Mag. .Nat. Ill.-t. L882, vol. ix. p. 219. 



-' Geo]. Mag. 1-ii.-,. vol. ii. p. 249. 



3 " Revision of the Fakieocrinoidea,'' Part. II. pi. xix. fig. G. 



4 Trans. St. Louis Acad. Sci. 1384, vol. iv. no. 3, p. 538. 



5 "Revision of the ralreocrinoidca, - ' Tart. I. pi. iii. fig. 5. 



