A MONOGRAPH OF THE EXISTING CRINOIDS 279 



Dr. Sixten Bock's expedition to Japan station 27; Misaki, Sagami Bay; 5-9 

 meters (diver); June 14, 1914 [Gisl6n, 1922]. 



Dr. Sixten Bock's expedition to Japan station 45; Bonin Islands, east of Chichi- 

 jima; 164 meters; July 31, 1914 [GislSn, 1922, 1924]. 



Geographical range. From Hong Kong northward to the Korean Straits and 

 eastward to Sagami Bay, Japan, and the Bonin Islands. 



Bathy metrical range. From the low tide mark down to 66 (?91) meters. Doctor 

 Bock's record of 164 meters represents the amount of line out, not the actual depth. 



Occurrence. Hara said that this form is very common along the Japanese coast 

 near Misaki, together with Comanthus japonica, and Mortensen (1920) noted that at 

 Misaki it is common in the same localities as the large Comanthus. 



It is common at Hong Kong. 



Preponderance of females over males. Dr. Edwin Kirk wrote that the preponder- 

 ance of females over males seems to be quite marked hi recent crinoids. Among 

 nearly 30 specimens of Comanthus japonica collected at a single locality at one tune 

 there were no males. The females in all cases bore large numbers of nearly ripe 

 ova. At the same locality Tropiometra macrodiscus likewise showed a very marked 

 preponderance of females over males. 



The locality referred to by Dr. Kirk is Sagami Bay, Japan, where the specimens, 

 which were identified by the present author, were collected by the late Dr. Bashford 

 Dean. 



Parasites. From the specimen recorded from Misaki by Dr. H. L. Clark 

 I removed no less than 93 rather large myzostomes (see Part 2, p. 654), and there 

 'is no way of estimating how many may have dropped off during or subsequent to 

 capture. These myzostomes were clinging to the disk and gonads, and were lodged 

 between the lower pinnules. In the basal quarter of the arm there was at least one 

 myzostome on every gonad. 



History.- This form was originally described in July 1895 under the name 

 Antedon macrodiscus by Jiuta Hara from a specimen taken at Misaki, Japan, in 3 

 fathoms. Mr. Hara said that Antedon macrodiscus resembles A. milberti in the 

 character of the tubercular radials and of the stout round segments of the lower 

 pinnules, as well as in the form of the brachials and in the intersyzygial interval. 

 But it differs from that species in the absence of spines on the cirri and in the discoidal 

 form of the centrodorsal. He noted that the number of cirri is different, although 

 this may be a trifling matter. To Antedon carinata it bears a certain resemblance in 

 the form of the centrodorsal, radials, brachials, and lower pinnules. But it differs 

 decidedly from that species in the absence of carination on the arms and on the first 

 two brachials. From Antedon rosacea (=bifida) it may be distinguished by the 

 difference in the intersyzygial interval, by the number of cirrus segments, and by other 

 characters. Mr. Hara said that this species has a certain alliance to the three species 

 named, but there are certain important points of difference by which it can readily be 

 distinguished from them. 



Upon the establishment of the genus Tropiometra in 1907 macrodiscus was re- 

 ferred to it. 



In April 1908, Dr. Hubert Lyman Clark recorded under the name of Tropiometra 

 macrodiscus and gave notes on a specimen from Sagami Bay collected by Alan Owston 



