1906.] NATURAL SCIENCES OF PHILADELPHIA. 503 



Praxillella tricirrata sp. nov. 



What appears to be an imdescribecl species of Praxillella is imper- 

 fectly represented by several fragments, one consisting of the head and 

 nine metastomial segments, of which the head and five segments are 

 in process of regeneration, a second of somites VI to XII inclusive, and 

 a third of the pygidium and eight preanal segments, the first five of 

 which are setigeroiis. 



This is a larger species than F. zonalis or P. clongata, having a 

 diameter of 3 mm. and an estimated length of about 150 mm. The only 

 known anterior end, being in process of regeneration, presents an ab- 

 normal appearance, somewhat approximating that of a Nicomache or 

 Lumhriclymene. The entire regenerating region, consisting of the 

 prostomium and six somites, has a length of a trifle more than 3 mm. 

 and barely exceeds the sixth segment. 



Head very short, with the cephalic plate and limbate margin scarcely 

 developed. There is a rather thick, short and broad palpode, and run- 

 ning back from it a narrower but, relatively to the width of the head, 

 broad median ridge bounded on each side by the deep and conspicuous 

 sensory clefts, which again are bounded laterally by the low folds from 

 which the limbate margins wiU develop, the whole forming a narrow 

 area scarcely exceeding one-third of the entire width of the head and 

 sloping steeply downward anteriorly. Mouth a rather large crescentic 

 opening bounded by the narrow^ furrowed persitomial lip. Peristo- 

 mium very short and uniannular. 



Somites II to VI are about twice as long as wide, slightly compressed, 

 distinctly biannular, decreasing slightly in diameter to the last, and 

 with the furrows, except ^^ which is obscm-e, well defined. No 

 distinct collars. The integuments of this region arc soft and delicate 

 and a careful examination discloses no developed setse, though the 

 setigerous glands are visible on some segments. 



The first normally developed segment (VI) is cylindrical, quite as 

 long as the preceding part of the worm, and 2-3 times as thick; VII 

 and VIII are c^uite similar; IX and X are united into one joint about 

 four times as long as wide and without any dividing furrow; XI is 

 slightly longer than VIII, and XII stiU longer. Except ^^ all 

 furrows in this region are deep and distinct; the segments somewhat 

 depressed and distinctly flattened ventrally. On VI, VII and VIII 

 the parapodia are situated one-third of the length of the segment from 

 its anterior end, and all of the area anterior to them is occupied by a 

 thick, whitish, glandular zone; a similar zone exists on IX, while on X a 

 thick, rugous, ventral, glandular area of triangular form extends 



