1903.] NATOEAL SCIENCES OF PHILADELPHIA. *77 



Triohobranobus bibr.nchUtas .p. nov. (PI. XXVII, llgs. S3-85.) 



The largest specimen has a length of 16 mm. for 29 somites the cau- 

 dal end bting Lent; the thoracic diameter is 2 mm.; almost double 



"tlfl- ..stricted to the region above the month, bilobate cor. 

 sisting of a pair of rounded tentacidiferous cushions incompletely 

 srLd posteriorly. No eyes. Tentacles -O' n"nierc»s foniimg 

 a ihick tangled mass above the mouth; they are of ^l°l""'^^-^'^^_ 

 ones which are bv far the most numerous, arising from the entire mar 

 g oUhe cushions, and much larger ones, the ends of which are often 

 broad and flat, whose origin is confined to the anterior and median 

 region of the cushion border. 



Peristomium simple, short above, much enlarged below to fo.m a 

 vefy Mgh thick lip the exact limits of which are uncertain ow.ng to 

 hTpartial protri'ion of the b™cal chamber. Connected .^^^^^^^^ 

 peristomium and probably peristomial in origin is a P-'jf ™J[^^^ 

 thin, delicately nerved, wing-like lobes, which arise o";ach ^'^^ from 

 ben ath the prostomium and extend prominently '^ ««^ ^^ ^. 

 riorly to a distance considerably exceeding the leng h of t^e Pro ° 

 mium. The remaining somites are regular and ^'^^'^-'■;^l^^^l^^2^ 

 out collars or lateral lobes to any of the anterior ones ; "S^J^ 

 of " annuli of which the anterior is usually the largest and bears the 

 r.Th thoracic region, comprising the first 20 ^"n.^'l^^^^ 

 and quite terete, the abdominal suddenly contracted to i the diameter 

 of he tirade, and flattened or even longitudinaUy grooved on he 

 ventral surface Two pairs of simple unbranched gills arise from the 

 doi m of somites II and III; they are slender and taperiijg and the, 

 length considerablv exceeds the greatest diameter of the body ihe 

 ttelci set g o,,;tori are elevated flattened tubercles, the uncigerous 

 tori vei^'imU and low; abdominal uncigerous tori also very small but 



quite conspicuously elevated. ^ =omites 



Slender seta; begin on VI and continue to XX, or foi 15 somites. 

 Thiyfo ma short vertical rank of 14 to 20, usually m pairs of 1 large 

 I^Il Ian seta. Set* almost colorless, slightly curved, tapering, 

 Tot er^h entire tip and narrowly doubly winged -;«>-. Uncm 

 also begin on VI, and occur on all the foUowing somites They are 

 Twavs Lnged in a single row, with their points directed forwa d 

 Id on the tho acic somiL, toward the dorsum; the series is slight y 

 :utd:ftheslenderse.on.^^^^^^^^^^ 



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