Sertularia. 
Z. HYDROIDA, 
129 
Polypidom 3 or 4 inches high, rigid, pinnate, lanceolate, dusky or 
blackish-brown, varnished. Stalk straight, compressed, jointed, with 
a series of alternate cells on each side : pinnee alternate, close, bifa- 
rious, several originating from each space between the joints of the 
stalk, simple, narrow at their origins, filiform, often gangrened at 
the apex. The cells are arranged in a close row along each margin, 
and directed alternately to opposite sides (Fig. 15) ; they are small, 
ovato-tu bular, short and adnate with a wide mouth having a small 
tooth on the outer edge. Vesicles unilateral, superior, elliptical or 
ovate, sub-pedicellate, smooth. 
Fig. 15. 
To this description, derived from specimens furnished by Messrs 
Bean and Embleton, I append that of Pallas, for Milne-Edwards 
denies the identity of his nigra with the British species (Lam. Anim. 
s. Vert. 2de edit. ii. 155) ; for which in my opinion there are no suffi - 
cient grounds, but a comparison of the descriptions will enable every 
one to decide for himself. “ Radices sunt tubi intestinuliform.es, lu- 
tescentes, implexi, usque ad pinnarum originem assurgentes. Stirps 
ad summum quadripollicaris, simplex , pennata, sublanceolata, testaceo 
nigra et tenuior molliorque quam tubuli radic antes. Rachis stirpis 
est tubulus crassitie fere calami avenacei, compressus, e planiusculis 
lateribus, et ipsis denticulatis, pinnas proferens. Pinnee s. ramuli 
