HEXACRINUS. 191 



Remarks. — One of the specimens in the Museum of Practical Geology is 

 Phillips's type, and the same specimen has also been figured by Austin under the 

 name of Hexacrinus melo ; Austin refers to Phillips's species as identical, but gives 

 no reason for changing the name. 



Hexacrinus depressus, Austin, also appears to be synonymous, as pointed out by 

 Schultze. 1 It differs chiefly in having a flattish tegmen composed of smaller plates 

 than those in the type specimen ; but the examination of a number of examples 

 shows that the tegmen varies very much in elevation, and that Schultze is right in 

 asserting that this character has no specific value. This variety is not uncommon ; 

 at least two of Mr. Vicary's fossils, and five of those in the Museum of Practical 

 Geology, belong to it. 



The typical arrangement of the tegmen appears to be as follows: — (1) a 

 central plate bearing an elevated central protuberance or boss, which according 

 to Wachsmuth and Springer is the posterior oral plate, and is surrounded by (2) 

 a cycle of seven almost equal polygonal plates, consisting of the four other oral 

 or proximal plates, two intercalated anals, and an odd plate of the anal system ; 

 (3) interambulacrals in two or three ranges, viz. a first row of three plates resting 

 on the first primary radials, a second row of two plates, and a third row (not always 

 present) of one plate ; (4) between each insertion of the arms and the proximal 

 cycle rows of two covering plates decreasing outwards ; (5) over the anal plate, 

 three rows of plates, two in each row. 



The ornamentation of the species is rather variable, though always bearing the 

 same general character of minute pustules giving a roughened appearance to the 

 surface to the naked eye. In one of Mr. Vicary's specimens the ornament is very 

 much finer and more confluent, and in the type it is coarser and less universal 

 than usual. 



One of the Torquay specimens from Lummaton has the distal margins of the 

 basals bordered by a row of small tubercles distinctly larger than the rest, and the 

 proximal border of the radials seems ornamented in the same way. 



The suture-lines are usually slight and narrow, especially in the larger fossils, 

 but occasionally they are decidedly deeper and wider. This may, however, be 

 partly due to injury in fossilization. 



Affinities. — I think that there can be no doubt that the Eifel fossils which 

 Schultze refers to this species are totally distinct from it. They have a larger 

 facet of attachment, more expanded basals, wider radials, and a coarser and entirely 

 different style of ornament. They should therefore resume the name H. granifer, 

 F. Homer, sp. 2 



1 1867, Schultze, ' Denksch. k. Acad. Wissensch. "YVien,' vol. xxvi, p. 191, pi. viii, fig. 5. 



2 1852, F. Romer, ' Verhaudl. d. Naturh. Vereins Rheinl.,' vol. ix, p. 281, pi. ii, fig. 1. 



