Dr. A. Philippi on the genus Serpula. 155 



of Serpula ; this character has moreover the advantage that it may 

 still be frequently observed in dried specimens preserved in mu- 

 seums. The structure however of the operculum is far more va- 

 ried than hitherto supposed, and several new subdivisions must 

 be made, of which the following are the characters : — 



A. Animal with opercula. On each side of the neck a short 

 membrane, broad above and narrow beneath, bearing seven fasciculi 

 of bristles, the upper one being generally directed anteriorly (this 

 structure is not known of Galeolaria). Serpula, Cuv. 



a. Operculum horny, shallow or infundibuliform, mmmd at 

 the margin, radiately striped above ; supported on a subconical 

 fleshy petiole. Serpula in the restricted sense. 



b. Operculum calcareous, forming a shallow disc, margin 

 entire. Placostegus, Ph. This operculum calls most to mind 

 that of a gasteropod. 



c. Operculum calcareous, conical, shortened or elongated, 

 without appendage. Vermilia, Lamarck. 



d. Operculum calcareous, hemispherical, with appendages 

 (which are interiorly hollow). Pomatoceros, Ph. 



e. Operculum calcareous ? horny ? consisting of an elliptical 

 shallow plate which supports on the hinder portion two rami- 

 fied horns, but on the anterior margin uncinate bristles ; the 

 branchiae are rolled up spirally. Cymospira, Savigny, Blainv. 

 The Serpula gig ant ea, 6m., which forms this division, I am not 

 acquainted with from the original essays of Pallas and Home, 

 but only from Blainville's ' Diet/ and from the copy of Home's 

 figure given by Blumenbach (Abbildungen Naturhist. Gegen- 

 stande, no. 67). 



/. Operculum horny, almost as in a, but provided on the 

 upper side in the centre with moveable points, which (at least 

 in one species) are likewise horny. Eupomatus, Ph. 



g. Operculum calcareous? obliquely truncated?; shell small, 

 always spirally wound?; branchiae constantly? composed of few 

 filaments. Spirorbis, Lamk. [The form of the operculum ex- 

 hibited by the figure in the ' Diet, des Sciences Nat/ 1. fig. 2. 

 is, precisely as in Placostegus, different from the form which I 

 have observed in another species.] 



h. Operculum calcareous, composed of very many pieces. 

 Galeolaria, Lamk. 



B. No operculum. The lateral membrane continued for half 

 the length of the body, equally broad. Apomatus, Ph. 



a. Branchiae spiral. Protula, Risso ; Spiromella, Blainv, 



M2 



