ORTMANN: THE CRAWFISHES OF THE STATE OF PENNSYLVANIA 353 



longer. Surface deeply concave, margins elevated and thickened, almost straight, 

 very little convergent toward the marginal spines. Mai-ginal spines well developed. 

 Acumen long, triangular, acutely pointed, about one third as long as the whole ros- 

 trum, sometimes slightly shorter or longer. Post-orbital ridges parallel, ending in a 

 sharp spine anteriorly. 



Surface of cara;pace finely punctate, and very finely granulate on the sides in old 

 specimens. Sides spinose. There are a number of larger and smaller spines on each 

 side on the hepatic region, and a few spines are found on the branchial region 

 immediately behind the cervical groove, of which one is generally much larger than 

 the others. (In most cases there are two distinct spines, one above the other, the 

 lower one the larger.) All the.se spines are well developed only in larger individ- 

 uals ; in young ones only two spines behind the cervical groove and one spine on 

 the hepatic region are present, l)ut tliese are visible even in the smallest specimens 

 at hand (25 mm. long). E.vternal orbital angle not marked, rounded off. Branchio- 

 stegal spine sharp and distinct. 



Abdomen longer than the carapace, slightly narrower than the carapace in the 

 male, sliglitly wider in the female. Antei-ior section of telson on the outer posterior 

 corners generally with two spines, but there may be from one to three ; the num- 

 ber of spines may differ on either side. Posterior section of telson semicircular, 

 slightly wider than long, and slightly shorter than anterior section. 



Epistoma with posterior part short and broad, almost three times as wide as long, 

 not plane, with a transverse groove posterior to the middle, and an anterior median 

 depression ; these are often united into a triangular or arrow-shaped depression. 

 Anterior section constricted at base, its anterior margin almost semicircular, with a 

 small median point, sliglitly varying in shape (sometimes it is subtriangular, some- 

 times the anterior point is ol)SCure), but its transverse diameter is always slightly 

 greater than the longitudinal. 



Antennula with a sharp spine on the lower margin of the basal joint. 



Antennal i^edunde with a sharp spine on the outer side of each of the two basal 

 joints. 



Antennal scale long, as long as the rostrum or even slightly longer, reaching to the 

 middle or the end of the terminal joint of the antennal peduncle. Outer margin 

 with a strong spine. Laminar part rather broad ; its margin more or less regularly 

 curved ; the broadest part is in the middle or slightly anterior to it. 



Flai/ellum, when laid backward, reaching to the fourth or even to the middle of 

 the fifth abdominal segment in the male ; in the female it generally does not reach 

 beyond the posterior margin of the third segment. 



