460 AUSTIN HOB ART CLARK, 



Fam. Mariametridae A. H. Clark. 



Genus Dichronietra A. H. Clark. 

 Dichrometra tenera (Hartlaub). 



Literature: See "The recent Crinoids of Australia", and "The Crinoids of the Indian 

 Ocean". 



Localities. Stat. 14; Sharks Bay, Freycinet Reach, west of 

 Mi dtlle Flat as far as the northern point ofHeirissou Prong; 

 11 16 meters; bottom at first sandy, later rock with coral; 12. IX. 

 (1 specimen). Stat. 22, Sharks Bay, inner bar, on the crest 

 of the bank; 6 9 meters; coarse sand, and sand and seaweed; 16. VI. 

 (1 specimen). ? Vicinity of Perth (1 specimen). 



Further Distribution. PortEssington; Bo wen; PortDenison; 

 Torres Strait; north of Cape Hills b or o; Thursday Island; 

 "Queensland"; Marshall Islands. 



Depth. Littoral. 



Notes. The specimens from Stat. 14 and 22 are both small and im- 

 mature; the latter has thirty-three arms 55 mm long; P 2 is 12 mm long. 



The specimen presumably from the vicinity of Perth is one of the 

 most extraordinary comatulids I have ever seen. It has fifty-seven arms 

 about 75 mm long, distributed among seven rays. It is not uncommon to 

 find specimens of Tropiometra picta from Rio de Janeiro with six rays, 

 but there is no published record of any individual of any other form, with 

 the sole exception of a specimen of Ptilometra macronema from Kangaroo 

 Island, which has more than the normal five outside, of course, of the 

 species of the primarily ten-rayed genera Promachocrinus and Decametro- 

 crinus. The details of these rays are as follows: 



[The enumeration of the rays commences with the one just to the 

 left of the (larger) anal area and follows the hands of the clock around 

 the disk.] 



1. A normal ray, though a trifle undersized; it bears eight arms about 

 70 mm long; all the division series are 2. 



2. Similar to the preceding, but with six arms, the two extra division 

 series being external; all the division series are 2. 



3. This post-radial series arises from a radial displaced ventrally so 

 that in their natural position the arms all lie over (ventral to) the arms 

 arising from the radials on either side ; the I B^ and I Br 2 are separated 

 by an almost invisible suture; the right branch (viewed ventrally) bears 

 five arms, the extra axillary being on the innermost side next the left 

 branch ; the left branch bears six arms, the left II Br series bearing two 



