Sept., 1917-] Fall: New Dytiscid^. 167 



Bidessus decoratus new species. 



Closely similar to the preceding species, but apparently distinct by the 

 following differences : Form just perceptibly less- stout, punctuation percepti- 

 bly less coarse and close above, and more noticeably so beneath ; sutural stria 

 feebly impressed but clearly enough evident in basal two thirds by the serially 

 arranged punctures defining a sutural interval which is abruptly, sparsely, very 

 finely punctate ; posterior elytral spot more elongate, and in the type inte- 

 riorly emarginate. The basal elytral stria is very nearly continuous with that 

 of the prothorax and is relatively a little longer than in quadripustulatus. 

 Length 2.1 to 2.3 mm.; width 1.15 to 1.3s mm. 



Arizona. Two specimens only are in my collection; the type 

 recently collected in the Catalina Mts. by -a correspondent of Dr. 

 Fenyes, who has kindly turned it over to me; the second example 

 bearing simply the label " Ariz." 



This species must be very similar to the Mexican Bidessus {Hy- 

 droporiis) fryi Clk., but if the statement made in the description of 

 the latter that " the elytra are covered sparingly with minute punc- 

 tures " is correct, it is hardly possible that they can be identical. In 

 decoratus the elytral punctures are decidedly coarse for so small an 

 insect, and are separated by scarcely more than their own diameters. 



Our three broadly ovate quadrimaculate species may be briefly 

 characterized as follows : 



Elytra without sutural stria, form more broadly ovate, punctuation coarser and 

 denser, notably so beneath ; pale elytral spots occupying much less than 

 half the entire area. San Bernardino Mts., So. Cal., 5,000 feet, 



quadripustulatus. 



Elytra with faint but traceable sutural stria, between which and the suture the 

 punctures are not appreciably finer ; elytral spots large, occupying as a 

 rule more than half the entire area. Ventura, Cal., near the coast, 



pictodes. 



Elytra with feebly impressed sutural stria defined by punctures, between 

 which and the suture the punctuation becomes abruptly very much sparser 

 and finer; elytral spots occupying much less than half the entire area. 

 So. Arizona decoratus. 



Bidessus ornatellus new species. 



Size and form nearly as in affinis, the elytra a little less pointed behind ; 

 upper surface subglabrous and strongly shining ; general color ochreous yel- 

 low, elytra fuscous with antemedian and postmedian zigzag or undulating 

 yellow fasciae, the apex yellow ; apical and basal margins of prothorax very 

 narrowly infuscate, at least medially. Antenna yellow with outer joints 



