154 BULLETIN OF THE 



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

 first two brachials, as in Act. Solaris. 



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

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

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

 water from which they were obtained. 



Although three fourths of the Actinometra 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 Actinometra? of the West Indies belong 

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

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

 have yet examined, the second and thud 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 articulated 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 Actinometra; in the Eastern 

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

 me are Act. Cumingii Mull, sp., from Malacca, and two or three unde- 

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

 " Blake " Comatulo?, 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 which the 

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

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



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

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

 according to the number of joints in the primary and secondary ray- 

 divisions and their modes of union. 



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

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

 A ni. ffagenii, Pourt.* It was obtained by the " Blake" on the Yucatan 

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

 at different depths between 75 and 291 fathoms; while Mr. Pourtalea 

 dredged it in greal abundance at several localities in the Florida 

 ■ Hull. .Mas. Camp. ZooL, VoL I. ETos. 6, H J V6L V. No. i, p. 214 



