208 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



Wheeler's analysis of the skeleton was given in an appendix. In 1927 Prof. Torsten 

 Gisl6n compared Chondrometra rugosa with his new species Perissometra aranea. 



Genus MONACHOMETRA A. H. Clark 



Antedon (part) von Graff, Challenger Reports, Zoology, vol. 20, pt. 61, 1887, pp. 8, 12, and following 



authors. 

 Charitometra (part) A. H. Clark, Smithsonian Misc. Coll., vol. 50, pt. 3, 1907, p. 361. 

 Pachylometra (part) A. H. Clark, Proc. Biol. Soc. Washington, vol. 22, 1909, p. 21. 

 Perissometra (part) A. H. Clark, Journ. Washington Acad. Sci., vol. 6, No. 17, 1916, p. 607. 

 Monachometra A. H. Clark, Journ. Washington Acad. Sci., vol. 6, No. 17, 1916, p. 607 (diagnosis; 



genotype Pachylometra fragilis A. H. Clark, 1912; range; included species); Unstalked crinoida 



of the iSt'boj/a-Exped., 1918, p. 173 (in key; range), p. 185. — Gislen, Vid. Medd. Dansk Nat. 



Foren. K0benhavn, vol. 83, 1927, pp. 2, 38; Ark. Zool., vol. 19, No. 32, Feb. 20, 1928, pp. 8, 9; 



Kungl. Fysiograf. Siillsk. Handl., new ser., vol. 45, No. 11, 1934, p. 20. 

 Monachomera Preston, Zool. Record for 1924, 1925, p. Echin. 27. 



Diagnosis. — A genus of Chart tome tridae in which the genital pinnules taper evenly 

 from the usually more or less broadened earlier segments to a delicate and slender tip, the 

 portion beyond the gonads being much longer than the gonads themselves; the outer 

 portion of the arms is rounded dorsally, sometimes with a slightly raised broad median 

 line; the oral pinnules are of about the length of the pinnules following, often slightly 

 shorter; the ossicles of the division series rise to a prominent, narrow, high, smooth, and 

 moro or less pointed synarthrial tubercle the profile of which forms a distinct and often 

 acute angle; the IIBr series are 2; there are 10-21 arms 90-250 mm. long; the cirri are 

 arranged in 10 or 15 columns on the centrodorsal ; and the cirri have 17-31 segments with 

 the opposing spine often bifurcate. 



Geographical range.- — From the northern Philippines southward to the Kei Islands. 



Bathymetrical range. — From 104 to 704 meters. 



Thermal range.— Two records, 7.2° and 15.0° C. 



Remarks. — The genus Monachometra as here understood includes, in addition to 

 M. fragilis the type species, M. patula, M. robusta, and M. flexilis, all of which were 

 previously placed in the genus Perissometra. Gislen in 1928 suggested that patula 

 should be referred to Monachometra, and at the same time definitely assigned robusta 

 to that genus. 



The species of Monachometra are most readily distinguished from those of Olypto- 

 metra by the smoothness of the division series and arm bases combined with the rather 

 prominent synarthrial tubercles, and the occurrence of IIBr 2 series only. 



Monachometra does not differ essentially from the earlier genus Chlorometra (=Dio- 

 dontometra Gisl6n) with which possibly it should be combined. 



History. — Monachometra was established in 1916 with the genotype and only species 

 Pachyhmii tra fragilis which had been described in 1912. Gisl6n discussed the genus in 

 1927 and described a second species, M. mortenseni (=Parametra orion). In 1928 he 

 discussed the genus at greater length tentatively adding Carpenter's Antedon patula 

 and definitely adding Carpenter's Anteden robusta. 



KEY TO THE SPECIES IN THE GENUS MONACHOMETRA 



a 1 . Brachials in the proximal portion of the arms with prominently raised distal edges; 10-21 arms 90- 

 190 mm. long (Philippines to the Kei Islands and the Sahul Bank; 104-385 meters). 



patula (p. 209) 

 a'. Brachials in the proximal portion of the arms with unmodified distal edges. 



