68 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 10 



branchia, O. nannognathus, O. pachytmema, O. proalopus, and O. socta) 

 of the above-named 30 species are included in Chamberlin's (1919, pp. 

 265, 295) keys; many of the others are very poorly known, through only 

 an original account. 



The collections of the Allan Hancock Foundation include 9 species 

 of Onuphis (as distinct from Nothria), of which 2 (O. microcephala and 



0. peruana) are believed to be new to science. 



Species of the genus Onuphis are typically very long, slender. Dredged 

 materials often include only a comparatively short anterior portion ; the 

 nature of posterior parts, therefore, has not been made known for most 

 species. Characters that have often been used for specific diagnosis include 

 (1) distribution of branchiae and their arrangement, (2) the maxillary 

 formula, (3) the character of anterior, prebranchial parapodia, and (4) 

 the type of tube. The first 2 are neither sufficiently specific nor constant 

 within a species to prove practical unless correlated with other characters. 

 In the collections I have examined, the microscopic parts of the first few 

 parapodia seem to provide one of the most accurate means for distinction 

 of species. The hooded hooks in these segments are apparently of several 

 kinds, as follows: 



1. Anterior hooks are entirely simple, falcate, lacking accessory teeth. 



A single species, O. teres Ehlers, is known. 



2. Anterior hooks are hooded, bidentate. This group includes: 



O. arjuandi (Mcintosh) 



O. ehlersi (Mcintosh) 



O. glutinatrix Ehlers 



O. litabranchia Chamberlin 



O. magna (Andrews), p. 70. 



O. pachytmema Chamberlin 



O. parva Moore, p. 70. 



O. socia Chamberlin 



O. williemoesi (Mcintosh) 



3. Anterior hooks include both bidentate and tridentate. This group 

 includes : 



O. dor sails (Ehlers) 



4. Anterior hooks include tridentate, or only rarely bidentate or quadri- 

 dentate, hooks. This is a large group, including most species of the 

 genus, and may be further divided as follows: 



a. Without composite spinigers or simple acicular hooks in anterior 

 parapodia, including: 

 O. eremita Audouin and Edwards, p. 75. 

 O. zebra Berkeley, p. 71. 



