294 ENTEROPXEUSTA FROM THE SOUTH PACIFIC, 



As shown in the text-figure, the proboscis-pores occur approximately at the level 

 of the neuropore, although the latter is subdivided in this species in the same way 

 as in Pt. biminiensis. 



The digitation of the cupule of the nuchal skeleton is also more extensive in 

 the present than in the preceding species. The stomochord undergoes fragmentation 

 in its nuchal region by the invasion of strands of skeletal substance, very much as 

 in Pt. carnosa. 



The collar nerve-cord in its middle portion consists of a sub-solid transversely 

 flattened band. There is a single root arising from the cord immediately in front of 

 the buccal orifice of the stomochord; it passes directly to the epidermis with which 

 it unites by a long anteriorly directed apical border. There is no dorsal septum near 

 the root ; it is limited to the posterior quarter of the nerve-cord. 



As already mentioned, the gill-pouches are produced ventrally into coecal pro- 

 longations. The gill-clefts are traversed by upwards of 50 pairs of synapticula. 



In the portion of the body which is characterised by the presence of the lateral 

 septa, namely, in the posterior branchial and genital regions, accessory genital ducts 

 occur laterally from the main series. The accessory gonads are arranged in a radial 

 manner in the genital pleurae and entirely fill the latter. The genital region of the 

 preserved animal was very brittle and the layers of the body-wall were in a disrupted 

 condition, but I have been able to satisfy myself, with reasonable certainty, that this 

 species agrees with Pt. biminiensis in having only lateral accessory gonads. 



The specimen at my disposal was a mature female. The ova were tightly packed 

 together, causing them to assume polygonal shapes, and they measured 11 mm. in 

 diameter. 



As at least two kinds of Tornaria have been recorded from the West Indies it 

 is important to note that, so far as known, all the Enteropneusta inhabiting the 

 shores of these islands belong to the family of the Ptychoderidae. 



