REPORT ON THE CRINOIDEA. 119 



that remains of them, while there are one or two slight indications of the second whorl 

 of cirri, the positions of which alternate with those of the first. The centro-dorsal has 

 increased considerably in thickness, as has also the joint below it, which has similar re- 

 entering angles, just as is the case in the infra-nodal joint in the stem of the Penta- 

 crinidse. Both of these larvse have quite low basals as compared with those of the other 

 species figured on the same plate, and especially Antedon hystrix? In this respect 

 they approach the Pentacrinidaa and the typical Apiocrinidae rather than Rhizocrinus 

 and Bourgueticrinus, which they resemble in the characters of the middle and lower 

 stem-joints. In the oldest larva, however, the basals are entirely concealed by the 

 centro-dorsal, which has now reached a considerable size, with the second whorl of cirri 

 well developed and even traces of a third, while there is only one discoidal joint below it. 

 (PL XIV. fig. 7). In Antedon multi 'spina, therefore, the basals become entirely concealed 

 before the end of the Pentacrinoid stage, as in Antedon tenella, though it is not the case 

 in Antedon rosacea. 



The youngest of the three immature forms of Antedon midtispina is considerably 

 more advanced than the oldest Pentacrinoid larva. Not only the basals, but also portions 

 of the first radials are concealed, and the first two pairs of pinnules have appeared, but 

 from the fifth to the twelfth brachials the arms are devoid of pinnules. In the still 

 older form, shown in PI. XIII. fig. 1, the first radials are only just visible externally, 

 though the second are relatively much longer than in the mature form. All the arm- 

 joints are provided with pinnules, though the lowest ones are quite small, that on the 

 second brachial being much more like its successor than is the case in the adult ; while 

 there is but little trace of any expansion in the lower joints of the genital pinnules. 



The spines of the cirri are present from the first, but those on the calyx, arms, and 

 pinnules do not appear till after the Pentacrinoid stage, while the lateral flattening of 

 the radials and lower brachials is one of the last characters to make its appearance. 

 This, of course, is only to be expected, for it is only when the arms become tolerably 

 wide that their lower portions come into close lateral contact. 



In the arms of the larvse, as in the pinnules of the adult, the covering plates are 

 supported upon imperfect side plates. These alternate very regularly with the sacculi, 

 which are relatively much more abundant than in the adult. 



12. Antedon echinata, n. sp. (PI. XXI. figs. 4, 5). 



Specific formida — A.-r-. 



Description of an Individual. — Centro-dorsal a low hemisphere with about twenty 

 cirri on its sides. These have some twenty-five joints, of which the fifth is longest, with 

 a slight dorsal projection at its distal edge which becomes a spiny keel in the short later 



