146 THE ANNELIDA POLYCHAETA. 



the tentacles of capitata are proportionately more slender; the first tentacu- 

 lar cirri are relatively much smaller and the dorsal tentacular cirri of the third 

 somite decidedly longer while the ventral cirri of the same somite are cylindri- 

 cal and truly tentacular instead of thin and foliaceous. The notocirri and neu- 

 rocirri of parapodia in the middle region of the body are relatively to their 

 lengths much broader, and the difference in size between notocirrus and neuro- 

 cirrus of a given parapodium is less. 



Rhynchonerella a. Costa. 



Ann. Mus. zool. TTniv. Napoli, 1862, 2, p. 168; Greeff (ad. part, gracilis), Nova acta Acad. Caesareae 



Leop.-Carol., 1876, 39, p. 57. 

 Callizona Greeff, Ihid., p. 56; Apstein, Ergebn.Atlant. Ocean *** Plankton-exped., 1900, 2, H. b., 



p. 16. 



Key to Species. 



a. One pair of tentacular cirri much exceeding the others in length R. cincinnata (Greeff). 



aa. One pair of tentacular cirri not thus much exceeding the others. 



h. Two pairs of tentacular cirri (on somites II and III) subequal and clearly longer than the others. 

 c. The first parapodia with more than two stout setae. 

 d. The stout setae simple. 



e. Notocirri of first parapodia not longer than the others R. mobii (Apstein). 



ec. These notocirri longer than any others R. melanopthalma (Greeff). 



dd. The stout setae composite. • 



e. The appendage of the stout setae robust and serrate R. setosa (Greeff) . 



ee. The appendage of the stout setae fine and smooth. 



/. Stout setae of first parapodium twelve; lower paired tentacles slender, not unusually 

 enlarged; notocirri not attaining ends of neuropodium, distally rounded. 



R. gruhei (Greeff). 

 //. Stout setae of first parapodia four; lower paired tentacles greatly thickened ; notocirri 



always surpassing the neuropodia, their tips acute R. pycnocera, sp. nov. 



cc. The first parapodia with only one or two stout setae. 



d. Cephalic tubercle very large; stout setae simple R. gracilis Costa. 



dd. Cephalic tubercle moderate in size, or small. 



e. Anterior neurocirri broadly ovate, distally rounded; stout setae composite; body plump. 



R. angelini (Kinberg). 

 ee. Anterior neurocirri narrow. 



/. Notocirri of middle somites cordate; dorsal tentacular cirri of third somite longer than 



those of the second; stout setae simple R. henseni (Apstein). 



//. Notocirri of median region narrowly elliptoacute to ovate-lanceolate; dorsal tentacular 



cirri of somites II and III equal in length R. parva, sp. nov. 



bb. The tentacular cirri gradually increasing in length from the first to the third pair. 



R. japonica (Izuka). 



Rhynchonerella cincinnata (Greeff). 



Callizona cincinnata Gueeff, Nova acta Acad. Caesareae Leop.-Carol., 1876, 39, p. 71, pi. 5, fig. 56-59; 

 Apstein, Ergenb. Atlant. Ocean * * * Planlcton-exped., 1900, 2, H. b., p. 16. 



This species has been previously known only from the type-specimen which 

 was taken at the Canary Islands. The specimens here recorded are smaller 



