1907.] XATIRAL SCIENCES OF rHILADELriH A. 199 



enclosed in a delicate hood. On VI from 4 to 6 sessile s]:)ines are 

 arranged in a slightly oblique series, diminishing in size from above 

 downward. They (figs. 16 and 23) are pale yellow, rather slender, the 

 blunt tips rather strongly hooked, a prominent subterminal s]>ur on 

 one side, and a smaller one often on the other. Cluard setae (fig. 15) form 

 a row anterior to and alternating with the spines; when unworn they 

 are broadly bilimbate at the end with a delicate and elongated mucron. 

 Overlapping the anterior-most spine from the dorsal side are 2 or 3 

 much larger bilimbate setae (fig. 14), abruptly bent and either truncate 

 or mucronate at the tip. A ventral posterior tuft beneath the last 

 spine contains 4 or 5 much more delicate, nearl}- straight setae, closely 

 resembling the guard setae. 



Color of intestine usually pale yellow; body walls translucent, with- 

 out pigment; blood red, coloring the gills and other parts. 



Known from the region about Wood's Hole only. Uncommon. 

 Usually taken in association with colonies of Amarcecium jyellucidimi 

 in 7-17 fathoms in Mneyard Sound. Less often on piles among 

 Cynthia in Little Harbor and with Polydora colonia at Mneyard 

 Haven. 



Type Coll. Acad. Nat. Sci. Phila., No. 2,338. 



A specimen taken on July 14th contained nearly mature eggs. 

 Polydora colonia sp. nov. 



Form elongated and very slender, resembling P. anoculata and of 

 about the same size or rather smaller. Number of somites unknown. 

 Length of head and 38 somites 6 mm., width at ^T 3 mm. Depressed 

 anteriorly, subterete farther back. 



Prostomium (Plate XV, fig. 18) elongated ; anterior half with straight 

 sides and of nearly uniform width, posterior half tapering into a nuchal 

 ridge which ends in a blunt point at the posterior margin of IV; anterior 

 margin broadly rounded, entire or slightly emarginate. Eyes usually 

 totally absent, but occasionally a small collection, or two, of pigment, 

 as in the specimen figured. 



Peristomium united with prostomium and somite II, forming a 

 simple posterior lip and a pair of prominent lateral cephalic lobes much 

 shorter than prostomium. Tentacular cirri attached to dorsum of 

 lateral cephalic lobes, not constricting prostomium. The basal half 

 has the usual structure and .proportions, but the distal half, probably 

 owing to maceration, is very slender and elongated, the total length 

 being about 7 times the width of \1 (fig. 18). The next four segments 

 are very short and much depressed; \1 is nearly[^as long as the three 

 preceding segments, strongly convex and furrowed laterally, widest 



