A MONOGRAPH OF THE EXISTING CRINOIDS 333 



the third pair of pinnules have keels on their second and third segments. He did 

 not regard this variation as of any importance, though he thought that the entire 

 absence of a keel on the 2 lowest pinnules (P] and PJ is a good distinctive character 

 of the type. 



He noted that other points in which the types of Solaris and imperialis and the 

 specimen from Hong Kong all agree are the unusual size of the lower brachials, which 

 may be as much as 5 mm. wide, and also the shape of the segments 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 segments are more 

 than twice as broad as long, and although this disproportion gradually decreases it is 

 only quite at the extreme end of the pinnule that the segments become anything like 

 square. This peculiarity is, of course, most marked in the lower pinnules, but it is 

 not until well on into the second third of the arm that the middle segments of the 

 pinnules begin to be at all longer than broad. 



Carpenter therefore considered that what may be called the special marks of 

 Solaris are: Cirri X-XV, 20-24; brachials and pinnule segments very broad; the 

 presence of expanded keels on the lower segments of the pinnules of the second pair 

 and some of the following pinnules, but the basal segments of the pinnules of the first 

 pair are not keeled. 



Carpenter noted that in the specimens from Cape York the plating of the disk 

 reaches the greatest development found in the comasterids. The whole of the large 

 anal area is covered with more or less scaly plates which become stouter and more 

 granular in the neighborhood of the subcentral anal tube. The sides of the deep 

 ambulacral grooves are bounded and supported by numerous smaller plates without 

 any definite arrangement. The plates immediately adjacent to the grooves are 

 extensively pierced by the water pores. Much of this armature extends beneath the 

 water vessels and corresponds to what Miiller called the subambulacral plates in 

 Cenocrinus. The plating ceases just within the circumference of the disk, so that the 

 perisome of the arms and pinnules is perfectly bare. 



The simple calcareous spicules and thin networks which occur in the less heavily 

 plated disks are especially abundant in the visceral layer of the peritoneum. This is 

 well illustrated by this species in which there is but little connection between this 

 visceral layer and the parietal layer lining the interior of the cup so that the entire 

 visceral mass is readily detached from the calyx. 



Abnormal specimen. Under the name of Actinometra strota Dr. P. H. Carpenter 

 mentioned a specimen dredged by the Challenger at Cape York in which one of the 

 second brachials on the right posterior postradial series bears two fully developed 

 pinnules instead of the arm and its own proper pinnule, so that it has the appearance 

 of an axillary. There is no disk ambulacrum corresponding to this undeveloped 

 arm. 6 



Localities. Singapore [P. H. Carpenter, 1879, 1888; A. H. Clark, 1911, 1912, 

 1913] (2. B. M.;H. M.). 



Billiton [P. H. Carpenter, 1888; A. H. Clark, 1913] (3, B. M.). 



China Sea [Hartlaub, 1891]. 



See vol. 1, pt. 2, pi. 24, flg. 1149. 



