MUSEUM OF COMPARATIVE ZOOLOGY. 15.3 



depth exceeded 200 fathoms. One may fairly conclude, therefore, that 

 'these anhnals are essentially inhabitants of shallow water. There is, 

 however, in one respect a considerable difference between the results 

 of the " Blake " and " Challenger " Expeditions. 



The " Challenger " species of Actinometra were nearly all obtained at 

 depths of less than 20 fathoms, the genus occurring at only one station 

 where the depth exceeded 100 fathoms. In 1878-79, however, the 

 *' Blake " dredged Actinometra 3 times at 7 to 50 fathoms, 10 times at 

 50 to 100 fathoms, 25 times at 100 to 200 fathoms, and 4 times at 200 to 

 300 fathoms, making in all 42 stations ; while Antedon was only met 

 with at 34 stations, at all but four of which the depth was less than 200 

 fathoms. 



As might be expected from the above facts, Actinometra is not only 

 represented by a larger number of species than Antedon, but it is also 

 individually more abundant. Comatuloe were especially plentiful at four 

 stations, viz. Nos. 155, 203, 262, and 269 ; and at all but the last 

 Actinometrce were the most numerous, both specifically and individually. 

 In fixct at Station 203 no Antedon was obtained at all, though at least 

 six species of Actinometra were met with. 



There are several points of difference between the general /aa'es of the 

 "Blake" and of the "Challenger" collections respectively, which sup- 

 plement one another in a very interesting manner. The great peculiarity 

 of the Caril)bcan fauna is the abundance of ten-armed CoriUttake repre- 

 senting both the principal genera. About two thirds of the Antedori 

 species and three fourths of the Actinometra; belong to this simple type; 

 while in the remaining species the rays rarely divide more than twice, 

 and in two species only is there a fourth division. In this respect the 

 contrast with the Gomatula fxuna of the Eastern seas is very marked. 

 Ten-armed forms of both genera are there decidedly in the m;nor>y, 

 especially of Actinometra, in which genus the rays may divide as often 

 as seven times, so that the number of arms falls very little short of two 

 hundred. 



The " Blake " collection from the Caribbean Sea may be fairly com- 

 pared with that made by the " Challenger " in cruising from Cape York 

 through the Banda and Arafura Seas to the Philippine Islands, and 

 thence southwards to the Admiralty Islands. About seventy species 

 were collected from this area, nearly all from depths less than 150 

 fathoms. The numbers of Antedon and Actinometra species are about 

 equal, but while half of the former are ten-armed, only three Actinometrce 

 ai'c equally simple. These three species all agree in having the second 



