102 TEREBELLKME. 



(a) Bristles with a simple point. Hooks having a rounded base which 



is prolonged in the anterior segments or throughout ; three to five 



rows of denticles on the vertex. 



Rows of hooks alternate, or double; two to three pairs of 



branchiae — Pista, Mgrn. 



Two pairs of subulate branchiae — Ettpista, Mcintosh. 



(b) Hooks clustered or thick-set with moderately long base, a ligament 



for fixing, three to five teeth on the vertex and from three to twelve 

 denticles (teeth) in all. Rows of hooks alternating in a certain 

 number of segments. One pair of branchiae with few branches — 

 Scione, Mgrn. 



(c) Two teeth and two transverse rows on vertex of hook ; two pairs 



of ramose branchiae — Nicolea, Mgrn. 



(d) Hooks with elevated crest, and base of moderate length. Two 

 teeth and two transverse rows of two to three denticles. Two 

 rows of hooks; three pairs of finely branched branchiae; seventeen 

 se tiger ous segments — Lanice, Mgrn. 



(e) Hooks not clustered, with a long base ; two teeth on the vertex ; 



two transverse rows of one to three denticles. Double row 

 of hooks facing each other, rarely simple and alternate ; three 

 pairs of arborescent branchiae; seventeen setigerous segments — 

 Polymnia, Mgrn. 

 2. Bristles commencing on the second or third segment, with simple points. 

 Hooks with a long base and a button ; two teeth on vertex, two transverse 

 rows of denticles or more. Hooks in a single row, retrogressive. 



(a) Bristles beginning on the third segment; two or three pairs of 



cirriform branchiae — Thelepus, Leuckart. 



(b) Bristles commencing on the third segment ; three pairs of cirriform 



branchiae — Grymoea, Mgrn. 

 Two or three pairs of subulate branchiae as in the Ampharetidae — Euthe- 

 lepus, Mcintosh. 

 II. Hooks pectiniform, without transverse rows of denticles on the vertex ; four to six 

 teeth. Double row of hooks in certain segments. Three pairs of arborescent 

 branchiae ; seventeen bristled segments — Loimia, Mgrn. 

 This classification does not seem to facilitate rapid work, and the variations in the 

 rows of denticles on the crest of the anterior and posterior hooks are considerable. The 

 form of the hook would appear to be of greater moment than the number of these teeth. 

 Other authors have increased our knowledge of this group, such as Ehlers, Gravier, 

 Fauvel and Wiren. 



The presence of otocysts in the Terebellida? was first pointed out by Claparede in the 

 larval Lanice conchilega, and in the young of another Terebellid by Agassiz, whilst Giard 

 and Nordenskiold worked at the same form as the first mentioned, considering it a special 

 form which Giard termed Wartelia. Meyer and Andrews also added to the knowledge 

 of the subject, whilst Fauvel (1909) carefully investigated it by serial sections, 



