164 THE ANNELIDA POLYCHAETA. 



and several forms are parasitic (C/. Eisig, Fauna u. Flora Golfes Neapel, 1896, 

 28; Treadwell, Bull. Amer. mus. nat hist., 1909, 26; Potts, Camb. philos. soc. 

 Proc, 1912, 16). Ichtyotomus, as a result of its parasitic habits, has been so 

 modified that Eisig makes it the type of the Ichthyotomidae. A few species 

 range to considerable depths, 600 fms., and one form, Syllis abyssicola Ehlers, 

 occurs at a depth of 1,380 fms. (C/. Ehlers, Annulata in exped. Porcupine capta 

 Ann. mag. nat. hist., 1874, ser. 4, 13, p. 295), and S. alternata Moore at 1,400 fms. 

 On the other hand, the epitokous stages of such forms as Autolytus are pelagic. 

 The fact that but little shore collecting was done by the Albatross during 

 the expeditions with which this paper deals accounts for the comparative paucity 

 of syUids and for the preponderance of pelagic forms among those secured, five 

 out of the six species being represented by their pelagic or epitokous forms. 

 Similarly, in the large annelid collection secured by the Challenger only eleven 

 species are syllids. Grube records fifteen species from the Philippines. On the 

 contrary, Ehlers (Festschr. K. gesellsch. Gottingen, 1901, p. 84) records twenty- 

 two species from the httoral region of the Magellan Strait. In the collection 

 of about one hundred and eighty-seven annehd species from Southwest AustraUa, 

 secured in the httoral region, or from but moderate depths, Augener found thirty- 

 eight species of SylUdae (Fauna Siidw.-Austr. Polych., 1913, 4, p. 68, 190 ff.), 

 a number in excess of those of any other family and rivalhng the forty species 

 secured by Langerhans in 1879 from the region of Madeira (Zeits. wiss. zool., 

 1879, 32, p. 514). The fewness of syUids in many collections from regions where 

 an abundance of species would naturally be expected is undoubtedly in large 

 part due to the fact that these annehds are mostly very small and require greater 

 attentiveness and special methods for their detection and preservation. 



Key to the Subfamilies and Genera. 

 I. Forms not parasitic or not permanently so. 



A. Ventral cirri, absent; cirri not articulated Autolylinae. 



a. All parapodia having dorsal cirri. 

 h. Dorsal cirri filiform or subulate, 

 c. Pharynx with a crown of teeth or trepan. 



d. Setae bidentate at tip Autolytus Grube. 



dd. Setae with tip of blade entire; palpi separated distally Sylline Grube. 



cc. Pharynx unarmed Autolytides Malaquin. 



66. Dorsal cirri not fiUform or cylindrical. 

 c. Dorsal cirri foliaceous or partly so. 



d. Tentacles and cirri long, exjjanded and foliaceous only distally Myriana Savigny. 



dd. Tentacles and cirri very short, leaf-like throughout Phyllosyllis Ehlers. 



cc. Dorsal cirri clavate Virchowia Langerhans. 



