MONOGRAPH OF THE EXISTING CRINOIDS. 275 



Hathrometra sarsii (hg. 1174, pi. 27). — In the lateral perisome of the pinnules 

 of this species Professor Sars found long, slender, slightly curved rods, with the 

 outer ends, in the distal outer portion of the lappets, expanded and pierced with a 

 few holes, and the inner ends, lying much more proximally, adjoining the border 

 of the pinnulars. Similar spicules occur in the brachial perisome from the first 

 appearance of the arms. 



Fariometra expUcata. — There are no deposits in the perisome of the pinnules. 



There are no spicules in the tentacles. 



Trichonietra cuhen»is (fig. 766, p. 362). — Each ambulacral lappet contains a 

 prominent long smooth rod, bent distally just before or at the middle, the outer 

 end of which bears several short spinules or processes, is slightly forked, or is 

 expanded with a hole surrounded by short irregular processes. 



There are no spicules in the tentacles. 



Trichometra vexator. — There are no deposits in the perisome of the pinnules. 



There are no spicules in the tentacles. 



T haumatonietra nutiix. — According to Mortensen there are no deposits in the 

 perisome of the pinnules and no spicules in the tentacles. 



Thaumatometra tenuis. — In the outer portion of the pinnules each ambulacral 

 lappet contains a long and rather stout rod, bent just before the middle, with the 

 outer quarter roughened, armed with scattered short spinules, or expanded and 

 perforated with several holes. 



Along their outer side the tentacles contain a broad and conspicuous band of 

 very fine interlaced spicules, which persists nearly to their tips. 



Family PENTAMETROCRINID^. 



Thaumatocrinus rugosus. — There are no deposits in the ambulacral lappets. 



The genital glands are covered with large, thin, filmy plates. 



There are occasional spicules in the outer side of the tentacles. 



Thaumatocnnua borealis. — On some pinnules each ambulacral lappet contains 

 a long but extremely narrow band-like plate, which reaches neai-ly to the edge of 

 the pinnulars. On other pinnules the lappets contain a long slightly curved rod, 

 slender and smooth, or thick and roughened throughout its length. Again, there 

 may be at the base of each lappet a very loose calcareous structure, consisting of one 

 or two, rarely of three, very large meshes of different sizes, usually accompanied by 

 a rod in the outer part of the corresponding lappet. 



The genital glands are inclosed in a thin calcareous film, consisting of a large 

 meshed reticulation with very slender bars. 



There appear to be no spicules in the tentacles. 



Pentnmetrocrinvs japonwus. — At the base of each of the ambulacral lappets is 

 a very loose meshwork of from 5 to 12 meshes, which are small near the pinnular 

 and rapidly become larger outwardly and distally, bordered with unfinished 

 meshes. The structure extends outwardly and distally from the point nearest the 

 pinnular, or from a point near the inner border. 



