NO. 2267. 



NEW BRANCHIOBDELLID WORMS— ELLIS. 



251 



Fig. 9.— Upper jaw of type- 

 specimen OF XIilONOGITON ORE- 

 GONENSIS OKEGONENSIS ELLIS, 

 FROM EUGENE, OREGON. 



The jaM's of A', oregonensis seem to have a 6-tooth plan, the upper 

 jaw having the six teeth symmetrically arranged in the order 

 e-B-a-a-B-c, that is a short, a long, two shorts, a long and a short. 

 The majority of the specimens of X. oregonensis oregonensis have 

 jaws of the formula 5-4, the teeth of the 

 upper jaw being c-B-a-a-B. The short out- 

 side tooth " c " suggests the absence of a 

 similar tooth on the opposite side of the 

 jaw to complete the 6-toothed plan. In the 

 6-6 type of X. oregonensis pectinatus the 

 teeth of the upper jaw are symmetrically 

 placed with reference to the median axis of 

 the jaw. being c-B-a-a-B -c. In the jaws of 

 this subspecies, however, the two teeth of order " a " are subequal 

 and the " /> " teeth, although longer than the teeth of the "<?" and 

 "a" orders, are relatively shorter than the "Z> " teeth in the jaws of 

 X. oregonensis oregonensis. For the specimens of X. oregon- 

 ensis pectinatus having the dental formula 7-6 the teeth of the 



upper jaw may be represented by the letters 

 c-B-a-a-B -c-d. In the jaws of the three worms 

 having 7-6 teeth, the extra tooth of the upper 

 jaw " d " was far enough out of line to show 

 a distinct lack of symmetry with reference to 

 the other teeth of the jaw. 



XIRONOGITON OREGONENSIS OREGONENSIS Ellia. 



Dental formula 5-4, varying from 4-4 to 

 6-5 ; the two small, median teeth of the order 

 " a " separating the tAvo tall teeth of the order " B " of the upper 

 jaw not subequal. 



XIRONOGITON OREGONENSIS PECTINATUS, new subspecies. 



Flate 12. fig. 3. 



Type.—Qnt. No. 17641, U.S.N.M., body length 1.3 mm., Sequal- 

 litchew Lake near the creek. Pierce County, 

 Washington, 4 miles south of Steilacoom, April 

 26, 1904, host not given. 



Paratypes.—Six Cat. No. 17642, U.S.N.M., 

 and two others, collected with the type. 



Dental formula 6-5, varying from 6-5 to 

 7-6; the two small, median teeth of the order 

 " a " separating the two tall teeth of the order 

 " B " of the upper jaw, subequal ; all of the teeth of the upper jaw 

 prominent, the differences in length of teeth small, the teeth of the 

 order " B " not conspicuously longer than the other teeth of the jaw. 



Fig. 10.— TTppER JAW OF TYPE- 

 SPECIMEN OF XIRONOGITON 

 OREGONENSIS PECTiNATUS EL- 

 LIS, FROM SEQUALLITCHEW 

 LAKE, WASHINGTON. 



Fig. 11.— LOWER jaw of type- 

 specimen OF XIRONOGITON 

 OREGONENSIS PECTINATUS 

 ELLIS, FROM SEQUALLITCHEW 

 LAKE, WASHINGTON. 



