272 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 5 



surrounding anus and extending ventrally as broad lateral shields (fig. 2) 

 which have heavily setose ridges on both sides of the anal region (figs. 1, 

 4) ; ventral to the anus the gnathos forms large ridgelike lobes (socii ?) 

 w^hich are densely setose especially on their median sides (fig. 1), and 

 from the undercut margins of these lobes a continuous sclerotinization 

 curves anteriorly and flattens out to form moderately sclerotinized plates 

 ventral to the anus (fig. 1). Vinculum shov^^n adequately in drawings. 

 Valves relatively simple and firmly fitted into the other parts ; outer sides 

 convex and terminating medianly in long, heavily sclerotinized prongs 

 (fig. 3) ; inner (median) and dorsal (costal) sides overhung and of con- 

 siderable depth (fig. 3 shows the true depth which is from vinculum to 

 the level of the median prongs) ; in addition, the costal margin has a more 

 heavily sclerotinized bar extending anteriorly into the body to articulate 

 with the ventral prong of the apodeme of the tegumen (fig. 2), and also 

 a narrower strip which passes medially at the lower (more anterior) level 

 to form transtillae supporting the membrane dorsal to the aedoeagus (fig. 

 1). No anellus (juxta). Aedoeagus (penis) attached only at its base and 

 sunk in a deep membranous pit in which it is freely movable (figs. 2, 3) ; 

 strongly sclerotinized, somewhat conical, opening broadly at its base for 

 entrance of the seminal ducts (this opening shown by dotted lines in 

 fig. 3, the lines dotted because all except the median dorsal prong of the 

 opening is beneath the membrane fomiing the aedoeagal pouch) ; no vesica 

 seen, the aedoeagus appearing as a hollow cone into which a pin may 

 readily be pushed. 



It seems needless to add that the depth of these structures results in 

 extensive foreshortening, and that the various views drawn must be com- 

 pared carefully. This is especially true of the relations of the costal bar 

 of the valve to the ventral prong of the apodeme of the tegumen. In fig. 1 

 these are represented as heavy bars of stipple, but the degree to which they 

 angle into the body (anteriorly) can be seen only by careful comparison of 

 figs. 1 and 2. 



