UNITED STATES AND MEXICAN BOUNDARY. 15 



P. depressus only by the mandibles and labrum being deeply rugous, and by the pos- 

 terior tarsi being not longer than the tibiae, while the latter in the male are densely 

 pubescent on the inner surface. 



P. corpulentus, niger nitidus, margine vix cyanescente, mandibulis vix rugosis, Ihorace transverso, 

 postice angustato, lateribus postice breviter sinuatis, angulis posticis rectis, elytris rotundato-ovatis 

 postice subacutis, lateribus valde rotundatis, humeris haud distinctis breviter carinatis, dorso asqualiter 

 couvexis, seriatim punctulatis (seriebus per paria approximatis); tarsis posticis tibiis haud longioribus. 

 Long. 145. 

 Laredo to Ringgold Barracks, Texas, Mr. Weise; Sonora, Mr. Schott. Only differs 

 from P. validusby the characters mentioned ; and eventually perhaps to be con- 

 sidered as a race of that species. 



P. costifer, niger nitidus, margine vix cyanescente, mandibulis rugosis, tborace transverso, postice 

 angustato, lateribus rotundatis ad basin brevissime sinuatis, angulis posticis parvis rectis, elytris ovali- 

 bus antice subtruncatis, postice subacutis, lateribus late rotundatis, humeris haud distinctis carina 

 mediocri, dorso sequaliter convexis, saepissime seriatim punctulatis, (striis per paria approximatis, inter, 

 stitiis saepe alternatim parum elevatis) versus marginem uni- vel bicostatis; tarsis posticis tibiis haud 

 longioribus. Long. 1-05-1-2. Tab .IV. fig. 11. 

 Lee. Proc. Acad. Nat. Sc. 7, 79. 



Creek Boundary, Dr. S. W. Woodhouse ; Laredo to Ringgold Barracks, and at Eagle 

 Pass ; Messrs. Schott, Weise and Haldeman. The sculpture of the elytra is very 

 variable, but all transitions are found in the series before me, between those with one 

 and those with two costse, those with smooth elytra, and those with punctures in 

 rows approximated by pairs, with the wider spaces more or less elevated. 



One specimen, (*97 long.) in default of more information may be for the present placed 

 here ; it was collected by Dr. Webb in Arizona. The elytra are without any trace of 

 costse ; the body is of a more slender form, being nearly as in P. elongatus Lee, but it 

 differs from that species by the humeral carina being shorter, and making with the 

 lateral margin an acute angle, while in P. elongatus the angle is rounded by the 

 carina bending outwards so as to make a curve with the lateral margin. Although 

 differing so much I think it more prudent to allow it to remain as a variety of P. 

 c o s t i f e r , until more specimens occur. Plate IV. fig. 11a represents an elytron. 



P. obsoletus Lee, is nearly allied to P. costifer, but the inner intervals be- 

 tween the rows of punctures are more distinctly elevated, and the rows are single. 



Agabus obsoletus, ellipticus, parum convexus seneo-niger, nitidus, conspicue reticulato-strigosus, 

 thorace lateribus obliquis late rotundatis, cum elytrorum lateribus angulum haud formantibus, antennis 

 pedibusque anterioribus piceo-rufis. Long. -33. 

 One male found at San Diego; differs from any other Californian species by its 

 elliptical body and scarcely perceptibly reticulate surface : the shape is nearly that of 

 A. punctulatus Aube, but the sides of the thorax are less rounded, and conse- 

 quently the approach to an elliptical form is nearer. 



