THE BEITTSBT SECONDARY EOCKS. 37 



paradoxus, Goldf.), but they are wanting in three others (including 

 G. conoideus), while we know nothing as to their presence or absence 

 in the two remaining species, since their centrodorsal pieces have 

 not been found detached from the radials. They occur in the three 

 Tertiary species described by Edward Porbes*; while Quenstedtf 

 describes them in Solanocrinus scrobiculatus, though Schliiter could 

 not find them in his own specimen of this species. I have met with 

 them, or their equivalents, in three fossil species that I shall de- 

 scribe further on, though not in a fourth. With respect to fossil 

 ComatuIcB, therefore, there is some ground for Schliiter's statement ; 

 but this is far from being the case for the recent forms, I have 

 dissected the calyx of thirty species, but have only found radial pits 

 in three of them. In at least two of these, viz. Ayii. rosacea (=A. 

 europceus^ Greeff) and Ant. celtica, their presence is very uncertain, 

 and in the third (a new ' Challenger' species) they are of a very 

 unusual character. On the whole, therefore, they are not so fre- 

 quent as might be inferred from Schliiter's description, only occurring 

 in sixteen out of forty-seven species which have been examined as 

 to this point. Then, again, these pits are not exactly blind saccular 

 extensions of the body-cavity, but merely the closed and slightly 

 expanded ends of the canals which are enclosed between the spout- 

 like processes of the rosette and the axial furrows on the inner faces 

 of the radials +. These axial canals are directly continuous with 

 the ventral furrows of the skeleton which lodge the dorsal portions 

 of the coeliac canals (parts of the body-cavity, it is true) of the rays 

 and arms ; and if their dorsal ends are not filled up by calcareous 

 tissue, as is usually the case in recent ComatuJce, they appear as 

 five openings near the centre of the under surface of the radial 

 pentagon. In any case, however, these openings of the axial canals 

 are closed by the ventral surface of the centrodorsal piece on which 

 the radials rest ; and this surface is sometimes, but rarely, marked 

 by the five radial pits corresponding to the openings (PI. Y. 

 figs. 5 a, 8 a). 



The last sentence in the passage from Schliiter's paper which is 

 quoted above seems to imply that were the calcareous tissue removed 

 which fills up the dorsal star (of fossil Comatidce) internally, the 

 radial pits would be complete perforations through the centrodorsal 

 piece. I cannot quite make out whether Schliiter believes that this 

 was ever really the case. If it were so (and I think it was so in 

 Ant. paradocca), then the canalicular extensions of the coelom which 

 end blindly in these pits (or sooner) must have been continued down 

 the larval stem outside the vascular axis ; for this axis, as 

 Schliiter himself points out, contained five vessels which expanded 



* " Echinodermata of the British Tertiary Deposits," Palaeontogr. See. 1852, 

 pp. 19, 20. 



t ' Petrefactenkunde Deutsclilands,' Band iv. " Echinodermeu," p. 179, Taf . 96. 

 fig. 57. 



\ See " On the Qenua ActinoTnetra,'* Trans. Linn. See. 2nd ser. Zoology, vol. ii. 

 pp. 77, 78, pis. 4-C), q, Q, & pi. 8. fig. 3, a.r.c, a.i.c ; and also H. Ludwig's "Boi- 

 trage zur Anatomip der Crinoideen," Zeitscbr. f. wiss. Zool. Bd. 28, Taf. xix. 

 fig. 74, Lr, U 



