1007.] XATl RAL SCIENCES OF rillLADELPHIA. 201 



tral ami slightly anterior to the lowermost is a second group of similar 

 but much smaller sctjc (fig. 20). 



Lives abundantly in colonies formed of soft mucoid tubes covered 

 with fine silt in the interstices of tunicates and sponges on wharf piles 

 in the harbor of Vineyard Haven, ^Massachusetts. Individual tubes are 

 less than 1 mm. in diameter and from 20-30 mm. long. Hundreds of 

 them are inextricably intertwined and cemented together with mucous , 

 forming masses 1 or 2 inches in diameter. Specimens taken at the end 

 of July contain large eggs which begin at somite XVI or XVII. 



The type is No. 2324 (Coll. Acad. Nat. Sci. Phila.). 



Unfortunately all of the numerous specimens were preserved in the 

 tubes and are more or less macerated and the posterior ends lost. The 

 seta>, however, and especially the spines and associated setae on VI, 

 are perfectly characteristic and serve to distinguish the species com- 

 pletely from any European or American species. 

 Magelona rosea sp. nov. 



Form very slender, body slightly depressed anteriorly, tapering very 

 gradually and subquadrate posteriorly. Length 40 mm., greatest 

 width 1 mm. Number of segments about 95. 



Prostomiimi and peristomium completely coalesced to form a head 

 (Plate XM, fig. 24) of a broad ovoid form, about ^ long erthan broad 

 l>ut capable of nnich greater elongation during life. A pair of dorsal 

 cephalic ridges, in contact metlialiy, extend for nearly the entire length 

 of the head, tapering to acute points anteriorly, and near the end 

 suddenly diverging, leaving a thin triangular area between. Anterior 

 and lateral portions of prostomium formed by a thin but rigid shovel- 

 like expansion marked on the dorsal surface by a number of delicate 

 raised sub-parallel lines. No prostomial appendages and no eyes. 



Peristomium dorsally consisting of the posterior portion of the 

 cephalic ridges and a pair of prominent lateral lobes, again subdivided 

 by a groove extending from the posterior margin; ventrally a simple 

 ring bounding the mouth behind. Tentacular cirri (fig. 24) arising 

 from the sides of the peristomium above the mouth and beneath the 

 margins of the prostomial plate. They are 8 mm. long, reaching 

 somite XX, delicate, and tapering, the lateral surface covered with very 

 fine and close transverse ridges, the medial with somewhat coarser but 

 still very small papillie which increase in length to the distal half where 

 they are as long as the diameter of the cirrus. Proboscis soft, bulbous, 

 protruded to half the length of the head and marked with numerous 

 fine longitudinal parallel ridges. 



Metastomium slender and of nearly equal diameter throughout, 



