CRINOIDEA 



37 



40-60 joints. Brachials usually smooth. Pinnuleg of about the 

 same length as P^. The genital pinnules with fairly large 

 calcareous plates in the side walls. 



This is a large and stout species, reaching an arm length of 

 200 mm. or even more. Colour in life 

 yellowish. It is infested with a large species 

 of Myzostorna, M. gigas Liitken, and also 

 with Myzostoma fimbriatum v. Graff. The 

 Entoproct Bryozoan Loxosomella antedonis 

 Mrtsn. also may occur on this species. 



The eggs probably are free ; the Penta- 

 crinoids are only rarely found and only a 

 few stages are known. The stalk- joints are 

 rather stout (Fig. 22). 



In British seas this species occurs only 

 in the cold area of the Faroe Channel. It 

 is an arctic species, probably of circumpolar 

 distribution, the form occurring in the North 

 Pacific being only regarded as a separate 

 variety, var. maxima A. H. Clark, which 

 grows to a larger size than the Atlantic form. 

 Bathymetrical distribution, ca. 10-1350 m. 



Subfamily Bathymetrin^ 

 5. Trichometra A. H. Clark. 



Centro-dorsal subcorneal, thickly covered 

 with small, crowded cirrus-sockets. Cirrus 

 segments elongate in the proximal half of 

 the cirrus, at least twice as long as the 

 median diameter, usually longer, squarish 

 in the distal part, these latter joints having 

 a sharply carinate dorsal surface which 

 projects more or less distally, giving a 

 slightly spinous appearance. Small cirri, 

 sometimes less than half the length of the 

 other cirri, consisting of 10-12 very slender 

 and much elongated joints, with greatly 

 expanded articulations, occur around the 

 dorsal pole of the centro-dorsal. Pinnule^ 



very slender, composed of much elongated joints, especially dis- 

 tally, with distal ends much widened. Brachials with strongly 

 produced and very spinous distal edges. 



Only one species known to occur in British seas. 



Fig. 22. — Pentacrinoid 

 of Heliotnetra glaci- 

 alis. (After Levin- 

 sen, Kara - Ha vets 

 Echinod.) x 6. 



