REPORT ON THE CRINOIDEA. 133 



Remarks. — This is a peculiar species for many reasons. In its general characters 

 it has many points of resemblance with Antedon basicurva, Antedon incisa, and 

 Antedon tuberosa ; but the sides of the basals and lower radials are not in close apposi- 

 tion and flattened laterally against each other as in those types, for they fall away 

 very rapidly from the dorsal towards the ventral surface, so that there is a considerable 

 space between every two rays, especially at the level of the articulations (PL XVI. 

 fig. 1). 



This is smaller on the surface than it is deeper down, for the lateral edges of the 

 joints are produced outwards like the projecting eaves of a roof. This condition is 

 extremely marked in the case of the second radials, which have the proximal edge 

 similarly produced so as to overlap the minute portion of the first radials which appears 

 externally. The relative shapes of the two outer radials vary extremely. Their usual 

 appearance is represented in PL XVI. fig. 1 ; but in some individuals the second radials 

 are rather more oblong and show hardly any indication of an incised distal edge, while 

 the axillaries are widely pentagonal. On the other hand the axillaries sometimes project 

 far backwards into the second radials, which thus have a deeply incised distal edge, while 

 the proximal edge is also much curved. 



In young specimens, such as that shown in PL XVI. fig. 2, a considerable portion 

 of the first radials is visible, but the projection of the edges of the next following joints 

 is almost as marked as it is in the mature individual. In the youngest specimen, with a 

 spread of about 80 mm., the external surface of the first radials is rather less wide than 

 that of the second, and a trifle more than half its length. It does not, however, increase 

 in size along with the corresponding parts of the two outer radials, but remains 

 undeveloped and is sometimes marked by small tubercular elevations like those on the 

 centro-dorsal, from which it is with difficulty distinguishable. These are situated in the 

 gap between the ventral edge of the centro-dorsal and the proximal edges of the second 

 radials, which project backwards so as to overlap and conceal them. 



The most striking character of Antedon accela, and the one which allies it most 

 closely to the Basicurva-grou]), is the great size, both of the pinnule-joints and of the 

 protecting plates on the genital pinnules. Even the second pair of pinnules are enlarged 

 for the reception of the genital glands, three of their middle joints being expanded ; and 

 a little further from the disk the fifth and the four or five following joints are flattened 

 and produced laterally, as shown in PL XVI. fig. 2, the proximal joint being often 

 much enlarged at the same time. This expansion is not almost entirely limited to the 

 outer side only as in Antedon incisa (PL XXI. fig. 2), but it is equal on both sides of the 

 medio-dorsal line ; and the ventral portion of these expanded joints is covered by an 

 arched pavement of strong plates, few in number but of large size, and often very 

 regularly arranged, as seen in figs. 1-3 of pi. liv. in Part I. These protecting plates 

 are much larger and better developed than in either Antedon incisa or Antedon tuberosa. 



