On the Scattered Skeletal Remains of Holothuroidea. 193 



the striae bent, which would, perhaps, indicate that the 

 surface was to some extent angulated (PL V., Fig. 12). 



The second of these peculiar bodies is club-shaped, convex, 

 and tapering downwards. The surface is either smooth, or 

 imbricato-striate, probably dependent on the state of preser- 

 vation (PL v., Fig. 11). 



4. The Nature and Affinity of these Plates and Spicules. — 

 On comparing the perforated plates (PL V., Figs. 1-4) with the 

 anchor-plates of the genus Synapta (PL VI., Fig. 10), a general 

 resemblance will undoubtedly be admitted. The nature and 

 appearance of the perforations, and the undulating outline, 

 when perfect, show this. On the other hand, the irregular 

 form, the number and arrangement of the holes, their simple 

 margins, and last, though not least, the entire absence of 

 any articular process for the anchors, show a decided de- 

 parture from the structure of the Synapta skeleton ; or, at 

 any rate, of the majority of the species assigned to that 

 genus. It appears to me there is a much closer resemblance 

 with the plates of such forms as Thy one fusus, Miiller (PL VI., 

 Fig. 13), or Thyonidium pellucidiir^i, Vahl (PL VI., Fig. 12), in 

 which the plates are figured by Diiben and Koren as simple and 

 irregular, with innumerable perforations, as in our specimens. 

 Our PL v., Figs. 5 and 6 — representing specimens from Wood- 

 end and Kinneil — clearly demonstrate the relation of the 

 anchors to the perforated plates, and in the former we again 

 meet with a departure from the Synapta type. The anchors 

 discovered by Mr Bennie are simple, without serrations of 

 any kind, one-fluked, and the proximal end of the shaft 

 terminated by an eye in the place of a small transverse 

 piece. Arguing from the researches of Messrs Woodward 

 and Barrett, we can do no less than accept these hooks as 

 those of the adult condition of the organism to which they 

 belonged. These writers have shown that in Synapta the 

 anchors are developed first, and afterwards the plates ;* they 

 say, " it is not until the anchors are completely grown that we 

 detect any trace of the anchor-plates." It follows from this 

 that the one-fluked hooks from the Carboniferous Strata are 

 adult, and hence a further divergence from the Synapta type. 



* Annals Nat. Hist., 1850, iii., p. 217. 

 VOL. VI. N 



