So BIOLOGICAL SURVEY OF 



fade in alcohol. In this paper the color is noted only when 

 it is distinctive and characteristic. 



Family Homorrhaphidae^ 



Halichondria Fleming 

 Halichondria panicea (Pallas) 



Bowerbanlv (1866, p. 229, 1874, pis. 39, 40), Ridley and 

 Dendy (1887, p. 2, pi. 2, figs. 2, 3), Lundbeck (1902, p. 17, pi. 9, 

 fig. 1. 



This species is hj far the commonest form taken in this 

 region and is found in a great variety of shapes. Most fre- 

 quently it is encrusting on rocks, shells, piles, etc., or forms 

 cushions or mats from which arise numerous low cones or 

 lobes, at the tops of which are oscula. Erect forms are infre- 

 quently found and these consist of tubes which are often 

 branched or partially coalesced to form flattened tubes with 

 oscula at their tips. 



Skeleton. In the encrusting forms the skeleton is confused, 

 while in the erect forms, although the skeleton is undoubtedly 

 confused as a whole, there is a slight tendency for the spicules 

 to be collected into fibers. 



Spicules. These are long, slender, gradually tapering, usu- 

 ally slightly curved oxea. The modal length of the spicules 

 varies greatly in different individuals, but in the encrusting 

 forms from this region the spicules range in size from .219 to 

 .511 mm., although the mode for the majority of specimens is 

 .438. In the few erect tubular forms the spicules are slightly 

 smaller, ranging from .324 to .405 mm., with a mode of .364. 

 Further study of these erect forms with their smaller spicules 

 and tendency to form indistinct fibers may show them to be 

 a variety distinct from the more common encrusting form. 



Geographical distribution. Common in Vineyard Sound, 

 Gulf of Maine, Gulf of St. Lawrence, and Davis Strait. It is 

 a very cosmopolitan species. 



^ The name of this family is not correct according to rule. — Ed. 



