516 ilE. P.H, CAKPENTER ON BE^V 



quite one of the best of any that he wrote. The large specimen 

 in the Vienna Museum, which was described by Miiller as Actino- 

 metra imperialist, was eventually referred by him to Lamarck's 

 typef. Both forms agree in their general characters, as I have 

 been enabled to determine by personal examination of their frag- 

 mentary remains — a privilege for which I am much indebted to 

 Dr, Steindachner and Prof. Perrier. The peculiar features of the 

 species are the characters of the lower pinnules. The first pair 

 are composed of numerous stout joints, the lowest of which are 

 stouter than, but not otherAvise different from, their successors. 

 But in the next pair of pinnules some of the lower joints have 

 their dorsal edges produced into well-marked keels. In Lamarck's 

 type these keels occur on the second, third, and fourth joints of 

 the pinnules on the third and fourth brachials ; while in the Vienna 

 specimen there is little or no keel on the fourth joint of the fourth 

 pinnule, and in the Hamburg one described above the third pair 

 of pinnules have keels on their second and third joints. I do 

 not, however, regard this variation as of any importance, though 

 I think that the entire absence of any keel on the two lowest 

 pinnules is a good distinctive character of the type. Other points 

 in which the Paris, Vienna, and Hamburg specimens'all agree are 

 the unusual size of the lower arm-joints, which may be as much 

 as 5 mm. wide, and also the shape of the joints composing the 

 pinnules of the sixth and following pairs. These are best seen 

 when the pinnules are dried, as they are then less concealed 

 by perisome. The lowest joints are more than twice as wide 

 as long; and though this disproportion gradually decreases, it is 

 only quite at the extreme end of the pinnule that the joints be- 

 come any thing like square. This peculiarity is, of course, most 

 marked in the lower pinnules ; but it. is not until Avell on into 

 the second third of the arm that the middle joints of the pinnules 

 begin to be at all longer than broad. 



What therefore may be called the special marks of Act. Solaris 

 are as follows : — 10-15 cirri of 20-24 joints ; arm- and pinnule- 

 joints very wide ; expanded keels on the lower joints of the 

 second pair and some of the following pinnules, but the basal 

 joints of the first pair are not keeled. 



Closely related to this large type are several others of smaller 

 size, and with fewer joints in the cirri, for which it is difficult as 



* Wiegmann's Arcbir, 1841, i. p. 141. 

 t Abhandl. d. Berlin. Akad. 1849, p. 248. 



