498 PROCEEDINGS OF THE ACADEMY OF [May, 



separated from one another. At the posterior end the metamerism 

 becomes obscure and the pygidium is truncated. 



Throughout the thoracic and much of the abdominal region the 

 uncinigerous tori are prominent. They begin on V, increase in length 

 to about XIII, remain practically uniform to about XX, and then very 

 gradually diminish, the last thoracic beuig about equal to the seventh. 

 As they become smaller and the ventral plates narrower, the tori are 

 carried more and more to the ventral surface, imtil in the middle ab- 

 dominal region they form bead-like swellings on a pair of muscular 

 ridges separated by a narrow median groove. Toward the posterior 

 end they^ are barely recognizable. Setigerous tubercles begin on IV, 

 and continue for from twenty-three to twenty-eight somites, tw^enty- 

 six being the most frequent number. They stand out prominently 

 from the dorsal end of the tori, especially the anterior ones, which bear 

 the greatest number of setae. Whitish glandular thickenings occur 

 just dorsadiof the setae lobes as far as somite XXII and prominent 

 nephridial papillae from VII to XX inclusive, and less prominently 

 and regularly on some of the succeeding somites. 



The setse (PI, XXXVIII, fig. 36) are noteworthy for the prominence 

 of their pennant-like fringed tips. They are arranged as a single row 

 of larger ones flanked on one or both sides by a row of smaller setae. 

 The former are straight or slightly cm'ved, with about one-half of the 

 exposed portion included in a loose sheath beginning abruptly and 

 tapering to the terminal pennant which begins as a sudden, much 

 flattened, very thin angulated expansion, curved strongly to one side, 

 tapered to a delicate point and prominently fringed on one margin. 

 The smaller setae are little more than one-half as thick as their exposed 

 parts, only half as long as the larger. Their form is generally similar, 

 but the' sheath is less evident and the tips broader, longer and more 

 abruptly bent to one side. Setae of the fu'st tuft are more slender and 

 of the posterior ones fewer than elsewhere. 



The uncini (PI. XXXVIII, fig. 37) are biserial and opposite on XI 

 and all following somites; uniserial on those anterior to XI. They 

 have a rather short base strongly convex below with a prominent toe, 

 a small posterior ligament process and a subrostral process with a 

 guard; the sinus is narrow with subparallel sides, the beak long, acute 

 and strongly hooked and the crest prominent, elevated and composed of 

 three or four transverse tooth rows, the lowermost large. On the 

 posterior somites the uncini are small, lack the posterior ligament 

 process and are consequently less angulated and they have a larger 

 number of teeth in the crest. 



