A MONOGRAPH OF THE EXISTING CRINOIDS 375 



Diagnosis.- — A genus of Coinactiniinae including species in which there are only 

 exceptionally more than XX cirri composed of not more than 25 segments of wliich 

 none beyond the firet, or first and second, are broader than long. The 10 arms may 

 be short and stout, greatly elongated and becoming extremely attenuated distally, or 

 very stout basally with the distal portion much prolonged and attenuated. The 

 elements of the IBr series and first 2 brachials are short and broad, and are in lateral 

 contact with their neighbors on either side. The ossicles in these 2 pairs are united 

 by synarthry, the line of union appearing externally as 2 very narrow triangles con- 

 verging to a common apex in the middoi-sal Une. The segments of the genital pin- 

 nules are short and broad, usually much broader than long in the basal half of the 

 pinnules, and more or less produced or carinate distally. There are no carinate 

 processes on the basal segments of the oral pinnules. 



Geographical range. — From Cape Lookout, N. C, southward throughout the 

 Caribbean Sea and as far as Rio de Janeiro, Brazil. 



Bathymetrical range. — From the shore line down to 508 meters. 



Thermal range.— From 8.22° C. to 26.17° C. 



Remarks. — In common with all other Atlantic comasterid genera when compared 

 with their Indo-Pacific representatives, the genus Comactinia represents a more 

 generalized type than Comatula, the genus to which apparently it is most closely allied. 



While plainly evident, the features characteristic of the subfamily Comactiniinae 

 are less strongly marked in Comactinia than in the other genera of the subfamily. 

 The presence of synarthries between the elements of the IBr series and first two 

 brachials give certain forms of the species of Comactinia very much the same general 

 appearance as certain species of Comissia, though their true relationship is at once 

 made clear by a glance at the highly characteristic cirri. 



In the bewildering diversity of arm structure, apparently in response to local 

 and restricted environmental conditions, the single species of this genus exceeds all 

 other crinoids. The forms in which this diversity is manifested are the same as those 

 seen in the more variable species of Comatula, especially in C. pectinata, but in Comac- 

 tinia they are carried to greater extremes, probably in correlation with its much 

 greater thermal and bathymetric range. 



COMACTINIA ECHINOPTERA (J. MUlIer) 



Plate 42, Figures 125-12S; Plate 43, Figures 129, 130; Plate 44, Figures 131-135 



(See also vol. 1, pt. 1, fig. 76 (lateral view), p. 129; figs. 241, 242 (ventral view of centrodorsal), p. 

 249; fig. 328 (cirrus), p. 281; figs. 408, 411, 412 (pentacrinoids), p. 317; fig. 421 (basal ray), p. 

 321; figs. 457, 4.58 (dorsal view of radial pentagon), p. 355; pi. 4, fig. 548 (orals); pt. 2, figs. 19, 

 20, 23, 24 (centrodorsal and radials), p. 15; figs. 412, 413 (pinnule tip), p. 255; figs. 632-634 

 (comb), p. 323; figs. 691, 692 (disk), p. 341; figs. 702-709 (disk of young), p. 341; fig. 941 (penta- 

 crinoid), p. 549; pi. 1, figs. 963, 964 (centrodorsal and radials); pi. 8, fig. 1019 (analysis of arm 

 division); pi. 17, fig. 1072 (comb)] 



Comatula echinoplera J. Muller, Monatsber. d. k. preuss. Akad. d. W'iss., April, 1840, p. 93 (inter- 

 syzygial interval); Archiv f. Naturgesch., 1840, vol. 1, p. 311 (intersyzygial interval). — Bronx, 

 Die Klassen und Ordnungcn der Strahlentliiere, II, Actinozoa, 1800, pi. 26, fig. 12 (calcareous 

 particles from the disk). — Dujardin and Hnrfi, Hist. nat. des zoophytes, fichinoddrmcs, 1S62, 

 p. 201 (synonymy; description). — P. H. Carpenter, Trans. Linn. Soc. (Zool.), ser. 2, vol. 2, 



