154 BULLETIN OF THE 



and third radials united by syzygy, and also a syzygy in each of the 

 first two brachials, as in Act. solans. 



This area averages about 10° farther south than that of the " Blake" 

 dredgings, and it is possible that the greater vegetative development of 

 its Comalulce may be due to the higher temperature of the shallower 

 water from which they were obtained. 



Although three fourths of the Adinometra species from the Caribbean 

 Sea are ten-armed, there is not one among them that recalls the Act. 

 Solaris of the Eastern seas, in which the second and third radials are 

 united by syzygy, and each of the first two brachials is a syzygial or 

 double joint. All the ten-armed Actinometrte of the West Indies belong 

 to a type which is but slightly represented in the Eastern hemisphere, 

 viz. that of Act. meridional is. In this type, as in every Antedon that I 

 have yet examined, the second and third radials are articulated together 

 by a vertical ridge on each of their apposed faces, at the sides of which 

 are large masses of ligament, but no muscular bundles. The first 

 syzygy in the arms is on the third brachial, while the first and second 

 brachials are articuiated together in the same manner as the second 

 and third radials, instead of forming a syzygial or double joint, as in 

 Act. Solaris. Nearly all the ten-armed Actinometrce in the Eastern 

 hemisphere belong to the Solaris type. The only exceptions known to 

 me are Act. Cumi7igii Miill. sp., from Malacca, and two or three unde- 

 scribed species from China, Japan, and Sumatra. Even among the 

 " Blake " Comatidce, in which the rays divide more than once, there is 

 very little variety of type. Either there are two distichals united by 

 ligament, or three, of which the axillary has a syzygy, the former case 

 being the more frequent ; and in six out of the nine species in wliich the 

 rays divide a third time, there is only one joint between the distichal 

 and palmar axillaries, to the latter of which it is united by ligament. 



On the other hand the Eastern Comatidce, with aliout the same num- 

 ber of arms (11-40), present several well-marked varieties of type, 

 according to the nmnber of joints in the primary and secondaiy ray- 

 divisions and their modes of union. 



Of all the Antedoii species dredged by the U. S. Coast Survey, that 

 with the widest range within the Caribbean Sea is the little ten-armed 

 Ant. Hagenii, Pourt.* It was obtained by the " Blake " on the Yucatan 

 Bank, and also at various stations between Dominica and Grenada, 

 at different depths between 75 and 291 fathoms ; while Mi'. Pourtales 

 dredged it in great abundance at several localities in the Florida 

 * Bull. Mus. Comp. Zool., Vol. I. Nos. 6, 11 ; Vol. V. No. 9, p. 214. 



