NO. 2267. JSfEW BRANCUIOBDELLID WORMS— ELLIS. 243 



or less, the extra tooth or teeth were placed asymmetrically, the five 

 principal teeth following the 5-toothed jaw plan. Jaws of species 

 having a dental formula of 6-6 or more approached the primitive 

 jaw type, e^specially as the teeth of 6-6 and 7-6 jaws were usually 

 more or less subequal. Among the species studied those having such 

 dental formulae possessed other primitive characters. It was also 

 found that the ventral jaAv usually bore a smaller number of teeth 

 than the upper, if both jaws did not carry the same number of teeth. 

 P^'or this reason the upper jaw was selected for purposes of com- 

 parison when but one jaw was used. 



From the sections studied the number and position of the major 

 pharyngeal diverticula and the presence or absence of buttress-like 

 .supports of connective tissue attached to the intersegmental parti- 

 tions were considered to taxonomic value. The major pharyngeal 

 diverticula may be seen to best advantage in sagittal sections (pi. 10, 

 fig. 2), although they may be located in good whole mounts of com- 

 pressed worms. These pharyngeal diverticula are not to be confused 

 with the slight invaginations of the pharyngeal wall, nor with a fold 

 in the pharj^ngeal wall near the posterior end of the pharynx (found 

 in many preserved specimens), due to the pushing forAvard of the 

 esophageal portion of the alimentary canal so that the anterior end 

 of the esophagus partly telescopes the posterior end of the pharynx. 

 The buttress-like supports of the intersegmental partitions are 

 found easily, if they are present in the specimen, in cross-sections 

 (pi. 10, fig. 1). The supports extend from the lateral portions of 

 the intersegmental partitions like braces, and lie more or less parallel 

 to the long axis of the body, so that in certain cross-sections they 

 appear to divide the cavity of the segment into three or more 

 compartments. 



XIRONODRILUS, new genus. 



-Branchiobdellid worms having: Two pairs of testes, one pair in 

 segment V and one pair in segment VI, each nephridium of the 

 anterior pair opening to the outside through a separate pore in the 

 dorsal half of segment III; spermatheca simple, not bifid; no acces- 

 sory sperm tu.be; three major pharyngeal diverticula, two dorsal 

 and one ventral; the intersegmental septa in the posterior half of the 

 body with butress-like supports more or less well developed; seg- 

 ments I to IX, inclusive, distinct, each segment being slightly con- 

 stricted anteriorly and posteriorly, so that its junctions with the 

 adjoining segments are well defined; at least nine distinct segments 

 A'isible in a dorsal view; the alimentary canal straight, its maximum 

 enlargement in segments III and IV; a somewhat concave, glandular 

 adliesive disk near each lateral margin of the ventral surface of seg- 

 ments VIII and IX; the anal opening dorsal or dorso-terminal; the 

 caudal sucker ventral ; and the borly distinctly depressed. 



