384 THE ANNELIDA POLYCHAETA. 



generally plunge into sand." And of Armandiella rohertianae: ''Like its 

 congeners this species is an active inhabitant of muddy sand, and it swims 

 through the sand swiftly, like an eel." 



They Uve upon organisms occurring in the medium they frequent. In the 

 sand or mud in their intestines are found sponge-spicules, diatoms, radiolarians, 

 Foraminifera, and the remains of various other organisms. 



Key to Genera. 



a. Lateral eyes present along the body and often on the prostomium; branchiae none, or but rarely 



present (Armandiella) Polyopthalminae. 



b. No cirri or branchiae present; somites distinctly separated. 

 c. Prostomium bearing a median process or tentacle in front; eyes with crystalUnes. 



Armandia Filippi, 

 cc. Prostomium without median process in front, rounded; eyes without crystalUnes. 



Polyopthalmus Quatrefages. 



bb. Lateral cirri or branchiae present; somites not distinctly separated Armandiella Mcintosh. 



aa. No eyes either on body or on prostomium, or rarely present, when present, branchiae also present; 

 branchiae present, or rarely absent. 



b. No branchiae (or cirri) present Opheliinae. 



c. Lateral segmental sensory pits present; the fascicles of setae sessile; body short and stout, 



grub-shaped Kesun, gen. nov. 



cc. No lateral segmental sensory pits; with distinct setigerous mamilae; body proportionately 



long and slender Tachytrypane Mcintosh. 



bb. Branchiae present. 



c. Branchiae pectinately branched; setae in preserved specimens not obvious (absent ?); anal 



cirrus single, proximally flattened Euzonus Grube. 



cc. Branchiae not pectinately branched, unifilamentous or rarely bifilamentous. 

 d. Some or all of the setae serrulate. (Body with a longitudinal ventral furrow). 



e. All setae finely serrulate Cassandane Kinberg. 



ee. Part of the setae smooth, part serrulate-spinous Nitetis Kinberg. 



dd. Setae smooth or simply limbate. (With or without a ventral furrow), 

 e. Body with a ventral furrow over all or part of length. 

 /. Body rounded anteriorly, grooved ventrally posteriorly; parapodia well-developed, 

 fascicles distinct, with mamilla between them. 

 g. Branchiae simple, filiform; no anal plate; body not abruptly separated into a tho- 

 racic and abdominal region Ophelia Savigny. 



gg. Branchiae all bifilamentous; an anal plate present; thorax sharply set off from abdo- 

 men Thoracophelia Ehlers. 



//. Body grooved ventrally over entire length; parapodia often weakly developed and with 



the fascicles essentially single, or with the separation between notopodials and neuro- 



podials weak and not accompanied l)y intervening mamilla. 



g. At the caudal end the body prolonged into a long, cylindrical or even somewhat clavate, 



tube at the tip of which is the anus, this tube usually finely furrowed transversely. 



h. Branchiae normally and uniformly developed over the entire or nearly the entire 



length; a distinct single median anal cirrus Omaria Grube. 



hh. Branchiae not uniformly developed. 



i. Branchiae very few, present only on the posterior median region; last pairs of 



setigerous processes not specially prominent Ammotrypanella Mcintosh. 



a. Branchiae more numerous, absent from the median region but unusually strongly 

 developed toward the ends; last (four) pairs of setigerous processes conspicu- 

 ously salient Urosiphon, gen. nov.^ 



gg. Body not with a long cyUndrical anal tube, the anal tube or scoop short. 



' Genotype, Arnmolrypane cylindrocaudalus Hansen, obpix., tail, and <Ti4>cov, a tube. 



