ARENICOLIDAE. . 393 



mally, but distally bearing short, hair-like teeth, or processes, along the sides. 

 In young specimens a second type of notopodial seta may occur, this being 

 limbate, with an exceedingly fine tip. The neuropodial setae are stout crochets 

 which are more or less cu^-ved and present a rostrate enlargement distally, 

 which ordinarily shows teeth along the distal edge and may or may not exhibit 

 a small subrostral spine suggesting the more prominent one, or the corresponding 

 tuft of hair, occurring in those of the Maldanidae. 



Five, six, or thirteen pairs of nephridia are present. In these there is the 

 usual open ciliated nephrostome internally. 



There are one or more pairs of glandular caeca opening into the posterior 

 portion of the oesophagus. The pharynx is globular. It is unarmed, though 

 it may have papillae tipped with chitin. 



Gamble and Ash worth give an excellent general account of the family. 

 (Quart, journ. micr. sci., 1900, 43, p. 419-569, pi. 22-29). 



The members of this group are more or less confined to shallow water. 

 They normally occur in and above the Laminarian zone. They frequent sand 

 and gravel in which they burrow, though the young forms are often found among 

 Algae rather than in the sand. The tubes of Arenicola marina, are U-shaped 

 and are stained on the inner side from the abundant yellowish green mucus 

 exuded by the skin. 



Spealdng of A. cristata as observed by him at Charleston Harbor, Stimpson 

 says: "It occurred in the third and fourth subregions of the littoral zone, living 

 in holes in the hard sand, which it had excavated to a length of two feet. These 

 holes were exactly adapted in width to the thickness of the animal, and were 

 not furnished with a lining of any kind. They extended obliquely downward, 

 being at first perpendicular, but curving so as to become almost horizontal; 

 the lower extremity was about one foot below the surface .... All the specimens 

 were found in their holes, with the anterior extremity downward, and when 

 taken were trying to escape by digging still further into the sand, which is 

 effected by continued rapid evolutions of the proboscis .... During the latter 

 part of March, we frequently observed in and about the holes of these worms 

 great quantities of a soft, transparent jelly, filled with minute brownish specks, 

 which proved to be eggs." (Proc. Boston soc. nat. hist., 1855, 5, p. 116.) The 

 arenicolids are limivorous. The spiral castings are to be seen on the surface near 

 the openings of their burrows. Branchiomaldane vincenii, a small form only 8-20 

 mm. long, lives in transparent mucus tubes attached to calcareous Algae at the 

 Canary Islands and in the English Channel. 



