50 MK. P. 11. CAErENTER ON THE GENUS ACTINOMETEA. 



As miglit be expected from the nature of the case, the range of variation of the 

 syzygial interval for the whole length of the arms is considerably greater than that of 

 the second interval alone. In the type and in variety 3 it differs also in a tendency to a 

 decrease rather than an increase in the length of the interval, which is more often two 

 segments than four, as is seen from Table VI. ; Avhile in the other three varietal spe- 

 cimens the tendency of the variation is to increase in the length of the interval, four 

 segments occurring much more commonly than two. With respect to these varieties, 

 however, it must be remembered that these conclusions are all based upon an examina- 

 tion of single specimens, which, as already mentioned, may in some instances be A'ery 

 misleading. 



(§ 32) The colour of Act. polymorpha is usually (in spirit-specimens) a yellowish 

 brown, which is much darker in the soft parts of the body than in the elements of the 

 skeleton. In variety '1, from Ubay, the colour is the same as that of the type, but con- 

 siderably darken-, so that the disk appears almost black. In varieties 1 and 2 the colour 

 is rather a greyish brown, which is considerably lighter on the ventral surfoce of the 

 disk and arms than on the dorsal skeleton ; and in variety 3 it is a somewhat reddish 

 brown. 



In varieties 2, 3, and 4< the dorsal surface of the skeleton is marked by a median 

 white line, with more or less defined dark borders, which commences on the radials, and 

 extends for some distance onto the arms. Its distinctness varies in difi"crent specimens 

 and in different arms of the same specimen ; but it is especially well marked in the 

 darkly coloured var. 4, as is seen in PL II. fig. 7. 



In an adult specimen of Act. liolymorpha the total diameter, including the arms, is 

 about 200 or 220 millimetres, of which about 20 millims. represents the diameter of the 

 disk alone ; but in one young specimen I found these two diameters to measure only 

 105 and 7 millims. respectively. The three specimens of varieties 2, 3, and 4 were of 

 about the same size as the type, but tlie single specimen of variety 1 was considerably 

 smaller, its longer diameter being only about 100 millims., and its shorter (that of the 

 disk) about 8 millims. This specimen, however, was, I believe, full-grown ; for it had 

 very large and well-developed genital glands ; while in the young and small specimen of 

 the type mentioned above, the size of which was about the same as that of variety 1, 

 the genital glands Avere scarcely developed at all. 



(§ 33) The manuscript name oi Act. armata has been given to the type of Actino- 

 metra here described, by Professor Semper, on account of the small spines with which 

 the segments of the arms and pinnules are fringed, more especially upon their dorsal 

 and aboral margins. As, however, this character is a very general one among the Co- 

 matidce, and as it is by no means so well developed in this type as in many others, I have 

 thought it advisable not to adopt Professor Semper's specific name, " armata," more 

 especially as it has been already employed by Pourtales to designate a new American 

 Antedon. Under these circumstances, I propose to designate this type as Act. poly- 

 morpha, having regard to the enormous amount of variation which I have found to exist 

 in nearly all its characters. 



I believe it to be very closely allied to, if not actually identical with, the type described 



