NO. 2267. 



NEW BRANCHIOBDELLID WORMS— ELLIS. 



253 



Tabije 4. 



Host and locality. 



Dental formulae. 



5-4 



5-5 



Cambants bartonii (Fabricius): 



Stoney Man Mountain, Virginia 



Blowing Rock, N orth Carolina 



Cambarus bartonii carinirosiris Hay; 



Cheat River, West Virginia 



Cheat River near the Pike^ West Virginia 



Chenowith Creek, West Virginia 



Cambarus bartonii robustus (Hay), Glennark Creek, North Rose, New 

 York. 



Cambarus bartonni subspecies, Cogars Mill, West Virginia. 

 • - -, Totals from Cambarus bartonii 



Cambarus obscurris Hagen: 



Trubies Rim, West Virginia. 

 Queens, West Virginia 



29 



Totals from Cambarus obscurus . 



Giand totals 37 



10 



As pointed out in the key to this genus the arrangement of the 

 teeth on the jaws of this species is diiferent from the western species, 

 X. oregonensis Ellis. In X. instabilius (Moore) the upper jaw', 

 when syniinetrical, has five teeth, c-B-a-B-c; that is, a short, a long, 

 a short, a long, and a short. If the upper jaw bears but four teeth, 

 as described by Moore and as found in over one-tliird of the speci- 

 mens examined, the tooth plan is c-B-a-B or B-a-B-c. This arrange- 

 ment may be explained by the loss of one of the " c " teeth. In some 

 of the 4-4 type the upper jaw seemed at first to be composed of a 

 long, a short, and two longs ; that is, two long teeth were contiguous 

 on one side of the jaw. By careful measurements it could be shown 

 in every case that the outer of the two contiguous long teeth was 

 shorter than the inner. This type of asymmetrical 4-toothed jaw 

 therefore has been considered a modified type of the 5-toothed jaw. 

 The elongation of the odd outside tooth of the " c " order ; that is, the 

 shorter of the two long contiguous teeth, in this type of 4-toothed 

 jaw probably represents a compensatory regulation, as the teeth of a 

 4-toothed jaw do not have the same alignment with the teeth of the 

 lower jaw as do the teeth of a 5-toothed jaw. 



Genus PTERODRILUS Moore, 1894. 



Pterodrilus Mooee, Proc. Acad. Nat. Sci. Phila., p. 449, 1894. 



One of the two species described by Moore at the time this genus 

 was designated was found in the collections examined, and two new 

 species have been added. With these additions this genus include^ 

 four species which may be distinguished by the following key : 



a.* Dorsal portions of one or more body segments bearing branched or digitate- 

 processes. 



