1902.] NATURAL SCIENCES OF PHILADELPHIA. 71 



In form the frous is subquadrate, with its auterior lateral angles 

 produced and embracing the obliquely truncated basal angles of the 

 epistoma. 



Laterally, where the frons meets the eye, the margin becomes 

 raised into a fine convex ridge or ocular bead, which is continuous 

 anteriorly wath the frontal ridge, posteriorly it winds around the 

 eye to become evanescent. 



Immediately within this bead is a fine sulcus or stria parallel to 

 it, usually well marked and varying in the degree of its width and 

 depth, and conveniently termed the ocidar stria. The ocular beads 

 and strite are common to all Bembidia. 



In all species of Bembidium there are developed other frontal 

 ridges and sidci; these reach their minimum of development in 

 some species of the variegatum group, where the ocular strioe are 

 bounded internally by rather broad convex longitudinal ridges, 

 w^hich in turn are limited internally by broad shallow grooves — the 

 internal sulci of Hayward — which pass more or less gradually into 

 the plane or convex central area of the frons. 



This condition is defined by Mr. Hayward in his paper treating 

 of the species of Bemhidium, Group XII (^variegatum), as " Frontal 

 grooves single, parallel or rarely very feebly convergent." In some 

 individuals these grooves and ridges are quite obsolete. 



In the different groups of species these grooves and ridges may 

 be parallel to or converge toward the median line. 



Generally the supraorbital setigerous punctures are placed in 

 small pit-like depressions or fovese upon the convexity of the ridges. 

 In some groups it is by the extension and coalescence in a longitu- 

 dinal direction of the foveas bearing the punctures that this single 

 broad, convex ridge becomes divided into two lateral moieties, form- 

 ing as a result two ridges separated by a sulcus — the external stdcus 

 of Hayward — the setigerous punctures now being found in the 

 bottom of this groove. 



This condition reaches its maximum development in B. sxilcatum. 



As long as the ridges and grooves are parallel to the median line 

 of the insect, they do not extend on to the epistoma (PI. Ill, figs. 

 2, 5 and 8, representative of Groups I to XIII, XV and XVIII 

 to XXI of Mr. Hayward' s paper) ; with convergency the exteu- 

 sion on to the epistoma does take place (figs. 1, 3, 4, (j, 7 and 9, 

 representative of Groups XIV, XVI and XVII of the above- 



