18 



combines the general appearance of Pleuroxus with the rostrum 

 of Rhypophilus, and the anterior and posterior marginal teeth of 

 Peracantha. The name is given from the shape of the rostrum. 



SPECIES 2. 

 Plate II. Fig. 11. 



Pleuroxus Straminius. sp. nov. 



Length, circ. 0.6. mm. Height, 0.85 mm. 



Post-abdomen slender, its dorsal side concave. Valves marked 

 by hexagonal meshes. 



The dorsal margin is not greatly arched. It forms a short but 

 well marked projection at its junction with the posterior margin. 

 A similar projection, not a tooth, is seen at the junction of the 

 posterior and ventral margins. Rarely, a very small tooth is 

 present there. The valves are marked by elongated, hexagonal 

 or irregular meshes. The rows run obliquely downward and back- 

 ward. The surface is also marked by the " stiitz-balken" and by 

 minute strise. These last are confined to the meshes and do not 

 cross the lines of reticulation. The post-abdoaien is long, slen- 

 der, somewhat curved, truncated at the end, with a large number 

 of fine, slender teeth on the dorsal row. The terminal claws 

 have the usual two spines, and are serrate. This last character- 

 istic is not always to be seen. The antennules have six or eight 

 sense-hairs besides the fLagellum. The eye is much larger than 

 the macula nigra. 



The rostrum of the male is much shorter than that of the fe- 

 male, the post-abdomen is more slender, and the terminal claws 

 are very slightly removed from its ventral edge. The vas defe- 

 rens thus opens between or slightly above the terminal claws. 

 Except for the regular sexual difference, it otherwise resembles 

 the female. Color, straw-yellow, opaque. 



P. straminius is most nearly allied to P. hastatus (Sars). The 

 females are nearly the same. They differ in proportions, hastatus 

 being higher proportionately. The lines of reticulation are hori- 

 zontal in P. hastatus, oblique in straminius. The former is " eine 

 der durchsichtigsten Species " (Kurz), while the latter is just the 



