94 Wifconmi Academy of Sciences, Arts, and Lelters. 



combines the general appearance of Pleuroxus with the rostrum 



of Ehypophilus, and the anterior and posterior marginal teeth of 



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



SPECIES 2. 

 Plate II. Fis. 11. 



Pleuroxus Straminius. sp. no v. 



Length, circ. 0.(j. mm. Height, 0.35 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 stride. These last are coiifined to the meshes and do not 

 cross the lines of reticulation. The post-abdomen 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 fiagellum. 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 



I 



