670 PATAGONIAN EXPEDITIONS: ZOOLOGY. 



SEMISCOLEX. 

 SEMISCOLEX VARIABILIS R. Blanchard. 



(Plates XLIX, Figs. 1-9; L, Fig. 12.) 



Except for the narrower prostomium and smaller mouth, the general 

 aspect is similar to Hczmopis, a resemblance which is especially striking 

 in the case of a quite small individual. The larger specimens are some- 

 what flattened posteriorly and rather sharply constricted at the region of 

 the sexual pores, anterior to which the body is narrower and nearly terete. 

 The arrangement of the eyes is shown in figures i and 7. The relative 

 position of the pigment cups and the direction of the axes of the eyes 

 are sufficiently obvious. The pigment cups of the first three pairs are 

 larger and more conspicuous than the others. No sensillae are discernible. 



Sixteen pairs of quite conspicuous nephridial ducts, appearing as short 

 tubes which pass obliquely backward through the integuments, open close 

 to the posterior margin of annulus b2 of every somite from IX to XXIV. 

 The anus is a conspicuous opening with lobed margins as in Hcemopis. 



Like Blanchard's types all three of the specimens studied by me have 

 the male genital orifice situated in the middle of XII bi. In the mature 

 examples it is a rather prominent four-rayed opening, slightly elevated on 

 a broad, low papilla, to support which the annulus is lengthened mesially. 

 In all three of Blanchard's specimens the position of the female pore dif- 

 fered, ranging from XII a2\b$ to XII b6, being separated from the male 

 pore, therefore, by two and one half, three and one half and four annuli 

 respectively. The intermediate condition was exhibited by an example 

 from Punta Arenas, Patagonia, and to this the three here described are 

 exactly similar. The female pore in all is a minute opening in a 

 depressed area situated at XII bjlbd. 



Annulation. The details of annulation of the best preserved mature 

 example are exhibited in Plate XLIX, figs. 2, 3, 5-8, and of the young 

 example in figure 4. 



Somites I, II, III and IV are separated by no distinct furrows, though 

 slight wrinkles may be caused to appear on the median part of the head 

 between the eyes by bending this region upward. These furrows, together 

 with the position of the closely crowded anterior three pairs of eyes, show 

 that the first three somites are uniannulate. Somite IV is apparently so 

 also, or else aj is very obscurely distinct, for, although the distance 



