THE APODOUS HOLOTHUBIANS 161 



extension to Newfoundland, Florida, and the West Indies. The reported oc- 

 currence at Point Barrow, Alaska (Murdock), would seem to indicate a cir- 

 cumpolar range. 



REMARKS. This is not only the longest-known but perhaps also the best- 

 known species, thanks to the careful investigations of Danielssen and Koren 

 (see their report, 1882, pp. 42-65 and 67-76, and Plates VII-XIII). It seems 

 probable that, in spite of their care, differences were emphasized and inter- 

 grading features neglected, so that no less than three species were made by 

 them out of a few specimens of this single form. Of course it is by no means 

 certain that Ankyroderma jeffreysii is identical with the Trochostomas, but there 

 is little reason to doubt it. The specimens of Ankyroderma reported have been 

 mostly under 50 mm. and 75 mm. is the maximum given. On the other hand, 

 Danielssen and Koren refer to specimens of Trochostoma 10 and 20 mm. long; 

 they do not say, however, whether the calcareous deposits of these specimens 

 were examined. There can be no question that borealis and oolitica are iden- 

 tical, for the latter is simply based on individuals in which the phosphatic de- 

 posits are excessively developed. The calcareous particles of all ages are fully 

 figured by Danielssen and Koren. 



MOLPADIA CONCOLOR. 



Trochostoma concolor Koehler and Vaney, 1905, p. 91; pi. v, fig. ix. Calcareous 



particles, pi. xm, figs. 16-18. 

 Trochostoma concolor caudatum Koehler and Vaney, 1905, p. 92. Calcareous particles, 



pi. xm, figs. 19-22. 

 Ankyroderma contortum Koehler and Vaney, 1905, p. 100. Calcareous particles, pi. 



xiv, figs. 8-13. 

 Ankyroderma intermedium Koehler and Vaney, 1905, p. 102. Calcareous particles, 



pi. xv, figs. 19-25. 



LENGTH. 125-150 mm., with a diameter of 45-60; in the adult, the caudal 

 appendage is not sharply distinct, but in young specimens it may be one-fourth 

 of the total length. 



COLOR. Grayish, more or less tinged and marbled with chestnut-brown, 

 orange-red, or bluish violet ; in adults the latter tint is very marked ; oral disc 

 and caudal appendage whitish. 



DISTRIBUTION. Reported from the coast of Kistna and Gulf of Bengal, 

 three stations of the "Investigator" (Koehler and Vaney). 



REMARKS. This species, though representing oolitica in the Indian Ocean, 

 appears to be quite distinct from the northern form. The specimens collected 

 by the "Investigator," although few in number, seem to show the transition 

 from young to adult form very well. It should be stated, however, that one of 

 the specimens described as A. intermedium was 115 mm. long and is therefore 



of maximum size for an Ankyroderma. The variety of color shown by these 

 11 



