MONOGRAPH OF THE EXISTING CBINOIDS. 



577 



pinnules of the third-thirteenth brachials have not as yet appeared ; the pinnule on the four- 

 teenth brachial is 2.5 mm. long and is composed of nine segments, of which the first and second 

 are twice as long as broad, " dice-box shaped," and the third-sixth much elongated, four times 

 as long as broad, with both ends expanded. The distal third of the seventh segment, as well 

 as of the following segments, has a series of denticles along the ventral median line, forming 

 an arm comb. The ends of all the segments are serrate. The following pinnules are essentially 

 similar. 



Color in alcohol, white. 



Collected off Adawara, Sagami Bay, on July 30, 1S95, by Professor Ijima. 



As in the case of the adults the pentacrinoids of the comatulids are all formed 

 upon the same general plan, but this plan admits of great variation in details. 



Size. The total length and the length of the crown of the pentacrinoids 

 differs greatly, as is shown by the following table : 



Whereas the records just given are for pentacrinoids of approximately full 

 size, the following are of pentacrinoids in various younger stages : 



From these figures it would appear that the length of the fully grown penta- 

 crinoicl in the Macrophreata ranges from 18 to 65-|- mm., the range in the Oligo- 

 phreata being from 3.3 to 15 mm. 



Were it not that Crotalometra porrecta is a deep-water type and that Hathro- 

 metra tenella occurs in 25 fathoms or less, it might be supposed that the length of 

 the column increased with depth; and were it not that Antedon inhabits water 

 quite as cold as that inhabited by Hathrometra tenella and H. sarsii, it would seem 

 that the colder the water the longer the column. 



