AND ITS RELATIONS TO RECENT COMATUL^!. 195 



III. — This leads us on to another rather peculiar form, viz. 

 that represented on pi. 88. fig. 9 of Quenstedt's ' Jura,' which I 

 reproduce (PI. IX. fig. 5). The centrodorsal is less ribbed than 

 in the type of A. costata, and the cirrhus-sockets relatively larger 

 but less numerous. The peculiarity of this form is that the 

 radials have no external surface at all. Their articular faces rise 

 directly from the upper surface of the centrodorsal, which bears 

 the whole of their dorsal surfaces, no part of these appearing 

 externally. They are more concealed than in any recent Comatulee, 

 in which their presence is usually just indicated by a line or a 

 ridge between the articular surfaces and the centrodorsal. At 

 the angles of the calyx are large basals partially separatiug the 

 lower angles of the radials from the centrodorsal, but encroaching 

 much more on the latter than on the former. 



IV. — The next type to be considered is an imperfect specimen 

 from Nattheim now in the British Museum (PL IX. tig. 0). Tbe 

 centrodorsal is essentially like that of A. costata, except that the 

 cirrhus-sockets are not quite so regularly disposed in ten rows, 

 and the ribs separating the rows are less prominent. The exte- 

 rior of the radials is very low, and it is not convex, as is usually 

 the case, but has an irregular groove running along it. Only 

 three of the five radials remain ; but only two basals are visible 

 at the four angles corresponding to them (PI. IX. figs. 6 «, 6 b), 

 and they do not project outwards at all. They are the smaller 

 ends of tapering rods which are seen sideways in fig. 6 c. Their 

 larger central ends are partially concealed by matrix, but seem to 

 have been in contact laterally, and to have received the lower ends 

 of the ventral interradial furrows which are seen descending 

 towards them in fig. 6 c. The upper angles of the calyx are but 

 slightly notched in correspondence with these furrows, and the 

 intermuscular notches of the articular faces are also very slightly 

 marked. 



The diameter of this specimen is 14 millims. Total height 9^ 

 millims. ; of radials 4^ millims. 



I propose to name the type Antedon canaliculata. 



V. — The next form to be considered is A. complanata, by which 

 name I distinguish a British-Museum specimen from Nattheim, 

 which consists of the basals and radials only without any centro- 

 dorsal attached (PL IX. tig. 9). The radials have an external 

 surface nearly as large as that of A. costata • and their distal 

 faces slope very much, so that the calyx has a flattened appear- 



