ORTMANN : THE CRAWFISHES OF THE STATE OF PENNSYLVANIA 395 



Oil tlie posterior lateral corners with one or two spines. Posterior section semi-ellip- 

 tical, distincth' wider tlian long, about as long as the anterior section. 



Efistoma with posterior part comparatively long, liardly one and one-half times 

 as broad as long ; transverse groove indistinct and close to posterior margin .• an- 

 terior median depression also indistinct, and thus the posterior part of the epistoma 

 appears ratiier flat and smooth. .Vnterior section constricted at base, semi-circular 

 or semi-elliptical or subquadrate, rarely with a median anterior point, often more or 

 less truncate anteriorly, or even slightly emarginate. Transverse diameter never 

 greater than longitudinal, as great as the latter or shorter. 



Antennula with a small tubercle on the lower margin of the ba.sal joint. 



Antennal peduncle without distinct spines or tubercles on the two proximal, 

 joints. 



Antennal scale short and small, slightly longer than the rostrum, and not reach- 

 ing beyond the distal end of the fourth joint of the antennal peduncle. Spine of 

 outer margin strong. Laminar j^art only slightly wider than the spine. 



Flagellum short, not reaching beyond the third abdominal segment in the male, 

 and not ])eyond the second sogniont in the female, but often hardly longer than the 

 carapace. 



First 'pereiopods (IM. Xi,, I'ig. 4) short, not very robust, not undergoing much 

 change with age, and not differing much according to sex. Hand ovate, broad and 

 depressed. Surface punctate. Inner margin of palm convex, with a single row of 

 distinct tubercles, larger proximally; occasionally tliere is a second, incomplete row 

 inside of and parallel to this. Outer margin smooth and n)unded proximally for 

 a short distance, but soon becoming angular and forming a distinct ridge along the 

 edge in the region of the base of the immovable finger. This ridge has a regular 

 row of deep punctures, giving the distinct appearance of serrations along the outer 

 margin of the hand. Fingers as long as, or slightly longer than the palm, .slightly 

 gaping at the base in both young and old individuals, straight. Outer margin of 

 moval)le finger with punctures, but very rarely with tubercles. Cutting edges with 

 a few iiicgular tubercles in tl)e proximal half Upper surface of each finger with 

 a low i-ilj, bordered by rows of punctures. 



Carpopodite slightly longer than wide, about as long as the palm, with a deep 

 longitudinal sulcus above. There is always a strong, more or less pointed, spine on 

 tlie inner n\argin. directed obliquely forward, and a strong, often spiniform. conical 

 tulK'ivle in the middle of the anterior margin of tlie under side, (rarely obsoleteV 

 The tubercle at the lower articulation with the hand is low and indistinct. Rarely 

 there are accessory tubercles, which, however, are never spiniform. The most fre- 



