STATE GEOLOGIST. 113 



Sp. lli. Plenroxiis prociirviis, Birge. 



(Plate E. Figs. 3, 4.) 



In size and general appearance this most interesting species is 

 similar to the above, and, especially, to P. deuticulatus. The gen- 

 eral form and even the details of structure agree almost to identify 

 with the latter. The structure of the posterior margin is like Per- 

 cantha, while the rostrum it bent abruptly upwards as in Rhypo- 

 philus. In small individuals the length is greater proportionally. 

 The lower margin is slightly convex or nearly straight, and fringed 

 by bristles v/hich are stroulgy pectinate; the anterior and lower 

 margins are toothed as in Percantha. The shell gland is more as 

 in the Daphnidie than most lynceids. The number of posterior 

 teeth is variable. The ephippium is as in P. deuticulatus. Length 

 O.iO mm. to 0.50 mm. Not rare, but less common than P. deuticu- 

 latus. The male post-abdomen is like that of P. denticulatus; the 

 rostrum is as in the female. 



Of the species following it may suffice to say that they are corpu- 

 lent, filth-loving representatives of P. trigonellus, P. adunctus and 

 P. bairdii, respectively, which have turned up their noses at a super- 

 ficial existence and buried themselves in the mire and debris at the 

 bottom of the pools. It. might be fanciful to assume that the curved 

 snout is used for "rooting," but the fact that these "Schmutz- 

 peterchen^' lynceids would fiud a long straight beak in the way is 

 suggestive. 



Sp. 13, Pleuroxiis (Rijjjophilus) glaber, Schoedler. 

 Pleuroxus personatus, p. e. mdeller. 



The shell is high and squarish, the fornices narrow, the beak 

 slightly pro-curved, the lower margin nearly straight, with two or 

 more teeth at the posterior angle. The antenujs have seven sette 

 only. The male is almost exactly as that of P. trigonellus. Length 

 0.55 mm. to 0.65 mm.; male 0.5 mm. 



Sp. 14. Pleuroxus (Ryjiophilus) peivsouatus, Leyclig. 



That this species is really distinct is by no means certain; how- 

 ever, it is stated that the shell is less regularly aud more markedly 

 reticulated, aud the markings lack the elevations described under 

 P. trigonollus, which are present in the previous species. It lives 

 in filth and covers itself with it. 

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