A MONOGRAPH OF THE EXISTING CRINOIDS 5 



protecting roof over the gonads. The genus Horaeometra is confined to the Caribbean 

 Sea occurring in water of from 159 to 479 meters in depth. 



' History —In Dr. P. H. Carpenter's Challenger Report published in 1888 the species 

 of the family Thalassometridae known to him were distributed among the Basuurva, 

 Spmifera, and GranuUfera groups of the genus Antedon. The family Thalassometridae 

 was established in 1908 to include the genera Thalassometra, Poecilometra, and than- 

 tometra the genus Stylometra being added later in the same year. In January 1909, 

 the family Thalassometridae was divided into the subfamilies Thalassometnnae, in- 

 cluding the genera Stylometra, Thalassometra, Stenometra, Stiremetra, Parametra and 

 Cosmiometra, all but the two first new, and Charitometrinae, the equivalent of the family 

 Charitometridae as now understood. 



In 1911 the subfamily Thalassometrinae was raised to farmly rank and Phlometra, 

 Pterometra, and Asterometra were transferred to it from the family Trop.ometndae. In 

 1914 the family Thalassometridae was divided into the two subfamilies Ptdometrmae, 

 including the genera Ptilometra, Pterometra, and Asterometra, and Thalassometnnae, 

 including the remaining genera. In 1934 Prof. Torsten Gislen raised the subfamuy 

 Ptilometrinae to family rank, leaving the family Thalassometridae as herein understood. 



KEY TO THE GENERA OF THE FAMILY THALASSOMETRIDAE 



a> Genital pinnules with no appreciable expansion of earlier segments. •„♦,„„„,„ 



' b' Irmsfat least in outer portion, laterally compressed and sharply carmate the carination p o- 



' du ed into a high crest or broad overlapping spine; arms more than 10 (or by individual 



variation 10) in number, the division series all 2; P, longer and proportionately stouter than 



P, though not otherwise different. . .., 



c> Division series and arm bases narrow and laterally compressed, gable, ik em cross section like 



' the outer brachials, the carination of the outer brachials being contmued proximally to 



the centrodorsal; cirri long and slender, 

 tf Arms 20 in number, 65-100 mm. long in fully developed individuals (from Tnnor and the 

 Moluccas north to the Bonin Islands and southern Japan; 141 t* 95 ^^^™^ ( 7) 



d> Arms 10-18 (usually 10-15) in number, usually 60-65 mm. long (from Port Denison, 

 Queensland, to Timor and north to southern Japan; 22-548 ^^^^ (p ^ 



A Division series and arm bases evenly rounded or more or less flattened dorsally, occasionally 



with a slightlv raised middorsal line. . , . , 



d« Cirri long and slender with more than 35 segments; division senes an lower brach.als 



usually more or less spinous, or at least bordered with fine spines ; 20-30 arms. 



e. Elements of the division series and lower brachials armed with numerous prominent 



' spines, at least along their borders; brachials beyond the proximal each , with a long 



thin, broad, and prominent curved overlapping spme (Canbbean Jg£££«g 



e* Elmnente ^ t hV d^on^nes^d'l^er^r^als smooth or with bands of minute 

 ' spines along their borders; carination of the brachials not produced into overlapping 

 pin s (from southern Japan and the Hawaiian Islands ^^SSiiSSSSi 

 westward to Ceylon, the Maldive Islands, and Saya de >«^^222T2 

 9 CirriThlrS'andsto'uVeVwith'noTmore'Vhan 35" segments; division series and lower bra- 

 chials smooth or with the lateral borders roughened or coarsely granular. 

 e i. S!^ at most 27 (usually 20-25) segments, short and stout; «n™ and arm 

 bases well rounded dorsally, appearing narrow and only shghtly flattened against their 



