160 THE APODOUS HOLOTHUEIANS 



A A. Anchors present, but if associated with more than a single plate, some of them have 



3 or 4 arms. 



B. Anchors with only 2 arms and associated with a single plate. 

 C. Anchor-plates large, about 400 /* long (plate x, fig. 23). 



Many tables with trifid base, the ends of each of the 3 arms expanded and 



perforated (plate x, fig. 24) BREVICAUDATA 



None of the tables with trifid base MARENZELLEKI 



CO. Anchor-plates small, about 130 /j, long (plate x, fig. 9). 



Tables with more or less irregular, often trifid base CONCOLOR juv. 



No tables at all present TRIDENS 



BB. Anchors commonly with 3 or 4 arms (plate x, fig. 25) POLYMORPHA 



MOLPADIA OOLITICA. 



PLATE X, FIG. 14. 



Chirodota oolitica Pourtales, 1851, p. 13. 



Molpadia borealis Sars, 1859, p. 174. 



Molpadia oolitica Selenka, 1867. 



Embolus pauper Selenka, 1867, p. 359. 



Trochostoma thomsonii Danielssen and Koren, 1878, pp. 229-256; pis. i-m. 



Trochostoma (Molpadia) boreale Danielssen and Koren, 1879, pp. 124-126, 137; pis. 



v and' vi, figs. 1-5. 

 ? Arikyroderma jeffreysii Danielssen and Koren, 1879, pp. 128-133, 135-137; pis. v 



and vi, figs. 11-19. 

 Trochostoma thomsonii maculatum Danielssen and Koren, 1882, p. 94; pi. xm, figs. 



5-6. 



Trocliostoma boreale Hoffman, 1882. 



Trochostoma (Molpadia) ooliticnm Danielssen and Koren, 1882. 

 Trochostoma oolithicum Lampert, 1885. 

 Trochostoma ooliticum Thel, 1886a. 



LENGTH. 100-335 mm., the diameter of the body about one-fourth as much;- 

 the caudal appendage short and not often abruptly distinct. 



COLOK. In life grayish green and violet are the prevailing colors, while 

 in preserved specimens dull gray and reddish or dark brown predominate; the 

 oral disc and caudal appendage are noticeably light-colored in contrast. The 

 exact coloration depends on the development of the phosphatic bodies; where 

 these are few, the general color is gray, with little brown, but when these are 

 abundant the color becomes more and more brown; in some specimens these 

 deposits become so numerous that the body is almost black. 



DISTRIBUTION. Eeported from numerous stations in the North Atlantic and 

 Arctic oceans, from Florida Eeef (Pourtales) and "West Indies (Theel) to Spitz- 

 bergen and north thereof (Ludwig) ; also eastward through Barents and Kara 

 seas to Cape Chelyuskin, Siberia (Stuxberg) ; in the eastern Atlantic it is not 

 known south of 62 N., while in the western Atlantic and Arctic oceans it is not 

 known north of Labrador or west of the Faroes. Its real home seems to be the 

 Arctic Ocean, north of Europe and western Siberia, with a long southwestward 



