G94 DR W. .B. CARPENTEK ON THE STRUCTTJEE, PHYSIOLOGY, AND 



extremities. Along the borders of these fun-ows there extend from the inner margin? 

 of the A'alvular folds Avhich fringe them, groups of delicate tubular tentacula ; each group 

 consists of three, of which one is peculiarly extensile. — The pinnules are borne on the 

 opposite sides of the successive segments of the arms, so that they present an alternate 

 arrangement. Those belonging to the basal segments of the aims (Plate XXXII. fig. 3) 

 assist in supporting the visceral mass, and during life they are observed to arch over 

 the disk (Plate XXXI. A) instead of projecting laterally like the rest; they are, more- 

 over, peculiar in being about twice as long as those which succeed them, and in being 

 entirely destitute of the tentacular apparatus. The succeeding pinnules, at the season 

 of reproduction, become turgid in consequence of the development of the ovaries or testes 

 in their substance, as already described by Professor Wyville Tiiomsox. 



3. When the visceral mass has been removed from the calyx, which is verj- easily 

 accomplished by tearing away the perisome that closes round its margin, we find the 

 floor of the basin (Plate XXXII. fig. 2) nearly smooth, but depressed in the centre, 

 where there is a passage through the calcareous pentagon formed by the union of 

 the First Radicds, which passage is occupied by a soft pedicle. This pedicle we shall 

 hereafter find to establish a connexion between the visceral mass and certain structures 

 contained in the cavity of the centro-dorsal plate ; and it is to be regarded as the residue 

 of the original Ci'inoidal axis. At a little distance from the central passage we see five 

 pairs of Muscles arranged pentagonally ; these pass between the first and the second 

 Radials. On the distal side of each of these we see two pairs of muscles, diverging from 

 each other; these pass between the third Radials and the first Brachials, — the second 

 and third Radials being connected by ligamentous union only (see § 37 and Plate 

 XXXIV. fig. 2). 



4. The Colour of our Antedon varies greatly. Commonly it is that which its trivial 

 name rosaceus implies ; but the crimson frequently deepens to a rich damask hue, espe- 

 cially during the breeding-season ; whilst it very frequently gives place to white on 

 portions of the disk and arms, so that the animal has a beautifully variegated aspect. 

 Sometimes, again, the predominant hue is a rich orange, and this may be variegated with 

 white or crimson, or with a bright sulphur-yellow. This last is often the fii'st colour 

 assumed by the Pentacrinoid larvte, when not far from the termination of their pedun- 

 culate stage. 



5. The Size of our Antedon also varies within a wide range. Its usual diameter from 

 tip to tip of its extended arms may be from 4 to 5 inches, but specimens exceeding this 

 limit are by no means uncommon ; and I have occasionally met with specimens as much 

 as 9 inches in diameter. As I am certain that these last were identical in structure 

 with the ordinary type, I cannot regard an excess of size as affording adequate ground 

 ;per se for specific difierentiation. 



