PALAEOTROPUS THOMSONL 



In the larger specimens of Palceotropus JosepMnce there is a slighl tendency 

 to the formation of very rudimentary bourrelets, The larger outer plates 

 of the actinal system carry a few minute miliary tubercles and spines, i PL 

 XXIII. Fig. 14.) () " the abactinal surface the ambulacral suckers arc 

 Blender, surmounted by a small indistinct sucker, the tentacles increase in 

 size towards the ambitus, and near the actinostome there arc four or five 

 large fimbriated tentacles in each ambulacra! area. 



The pedicellariae are mosl varied, representing types characteristic of the 

 Clypeastroids as well as the Spatangoids. On the actinal side there are in 

 the ambulacra, uear the outer edges, minute slender, long-stemmed, two- 

 jointed pedicellariae with small pear-shaped trifid head-. At the ambitus, 

 interspersed among the preceding, are short-stemmed, large-headed, stout 

 pedicellariae resembling the Clypeastroid types. In the hare interambulacral 

 spaces there are a few large-headed, short-stemmed, trifid pedicellariae, some 

 with short prongs, others with long crossing prongs. Scattered irregularly 

 over the abactinal surface are few distant triangular-headed trifid pedicel- 

 lariae, with long, slender stems, and short, flexible head-joints. The head-; 

 of these last pedicellariae are of two very different sizes, but otherwise they 

 do not differ. 



* Palaeotropus Thomsoni a \... 



Palaeotropus Thomsoni A. A.O. Bull. M. ('. /.. VIII.. No. l'. p. BO, 1880. 

 32 13' 25" N., ] g. 77° 2C 30" W. 233 fathoms. 



At Station 321 a single broken specimen of this species was collected, 

 which differs mosl strikingly from all the other specimens of Palaeotropus. 

 It is closely covered by uniform tubercles on the abactinal side. It has a 

 proportionally greater number of coronal plates, and a high test, with a 

 keeled posterior interambulacral median line. Apex more posterior than in 

 /'. Jbsephina . 



The color of the ti-t IS \ elloW isll W'llitc W hell ali\ e. The 1.1 I je /'. •/ ./>///, if 



are of a dirty greenish red color, and when young more pinkish. This 

 species is also remarkable for its broad, hare posterior lateral ambulacra on 

 the abactinal side, and for iis prominent keeled, very elongate actinal plas- 

 tron, and its longitudinally elongate anal fasciole, still very prominent at a 

 time when in /'. JosepMnce the posterior extremity has become flattened, and 

 the fasciole quite indistinct. 



