46 University of California Puhlications in Zoology [Vol. 18 



GENERAL DESCRIPTION OF THE POLYNOIDAE 



The Polynoidae are Mddely distributed, occurring in boreal, tem- 

 perate and tropical zones; in shallow waters and in depths beyond 

 3000 fathoms. A few species are cosmopolitan, occurring in all 

 oceans, but for the most part each particular area harbors its char- 

 acteristic species ; species common around San Diego Bay are not 

 found in San Francisco Bay, but their place is taken by other species. 



The Polynoidae were classified by the early workers as a genus or 

 several genera of Aphroditidae. The recent workers, however, with a 

 few exceptions, are following Kinberg's (1857) plan in classifying 

 the Polynoidae as an independent family. The Polynoidae resemble 

 the Aphroditidae in certain characteristics. In the first place, they bear 

 scales, or elytra, which are arranged in the same order as in Aphrodi- 

 tidae, occurring on segments 2, 4, 5, and on all alternate segments 

 to segment 23. Thence posteriorly the arrangement of elytra is less 

 regular. In the second place all elytroferous segments are devoid of 

 dorsal cirri. The peristomal segment bears the first parapodia. On 

 the other hand, the Polynoidae differ from the Aphroditidae in some 

 essential characteristics. The shape of the body of the Polynoidae 

 is more oblong than that of Aphroditidae, varying in length in dif- 

 ferent species. The lateral and the felt fibers are absent in Poly- 

 noidae. The parapodia are biramous and distinct from the main 

 body. The prostomium is bilobed and convex. The facial caruncle is 

 absent. The eyes, instead of being borne on peduncles, are placed 

 farther posteriad on the prostomial lobe. The base of the median 

 tentacle is inserted in the anterior fissure of the prostomial lobe. 

 Two additional lateral tentacles are present. The proboscis is mus- 

 cular and exsertile with a chitinous armature. The chitinous jaws 

 are strongly developed. The setae are of two or more kinds and are 

 more complex than those of the Aphroditidae. The nephridial papil- 

 lae open ventrally at the base of the parapodia. 



The shape, size, and color of the body of the Polynoidae may vary 

 according to the conditions and the environment in which the indi- 

 viduals live. Hence these characteristics do not always furnish a 

 reliable basis for classification. The following may serve as an illus- 

 tration. While at the Scripps Institution for Biological Research at 

 La Jolla, I had opportunity to compare specimens of Polynoe pulchra 

 which had been taken from different hosts. The specimens that came 



