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THE VOYAGE OF H.M.S. CHALLENGER. 
spine. In the older zooecia the peristome in front rises into a strong, conical, rostriform 
process, upon which occasionally a small avicularium (with a triangular mandible) is 
developed below the apex in front ; on many zooecia an immersed avicularium (with an 
obtuse duck-bill shaped mandible) directed obliquely downwards. Wall of zocecium crib- 
riform, the large perforations surrounded with a thickened border. Zooecia about 0 //, 02 
wide. Orifice 0" - 0075. 
Habitat. — Station 163b, Port Jackson 35 fathoms, hard ground (on a Carbasea). 
Off Marion Island) surrounding the stem of an Alcyonarian, but not attached in either case). 
Station 303, lat. 45° 31' S., long. 78° 9' W. ; 1325 fathoms, blue mud. Station 253, 
lat. 38° 9' N., long. 156° 25' W., 3125 fathoms (on a manganese nodule). Station 
313, lat. 52° 20' S., long. 68° O' W., 55 fathoms, sand. Station 315, lat. 51° 40' S., 
long. 57° 50' W., 12 fathoms, sand and gravel. 
The specimen from Station 303 is more delicate, and the different parts are much 
less developed. 
It might be a question whether the numerous forms that would come under § /3 should 
not be considered generically distinct from the fissured ones. 
Family XIX. Micropokellida;. 
Microyorellidcje (pars), Hincks, Brit. Mar. Polyz., p. 204. 
Escliariporidce (pars), Smitt. 
Celleporidce (pars), Johnst., &c. 
Membrcmiporidce (pars), Busk. 
Porinidce (pars), d’Orb., Smitt. 
Character. — Mouth semicircular or coarctate, with an entire straight lower border; a 
lunate fimbriated median pore. Zoarium erect and bilaminar, or crustaceous and adnate. 
[I have ventured to modify Mr. Hincks’ definition for the purpose of limiting it to such 
escharine forms as have a true lunate pore. Consequently, as here understood, it corre- 
sponds with Prof. Smitt’s genus Porellina (Florid. Bryoz., p. 27). As thus constituted it 
appears to me to form a very natural group, divisible into two or perhaps three genera 
or sub-genera, distinguished by the presence of a vibracular or of a quasi-avicularian organ 
on one side of the front sometimes absent ; and in part by the shape of the mouth.] 
The Family here contains the following genera : — 
§ a. Erect, bilaminar. 
1 . Flustramorpha , Gray. 
(1) Flustramorpha marginata (Krauss) (PI. XX. fig. 8). 
(2) Frustramorpha hastigera, n. sp. ? (PL XXI. fig 7). 
§ / 3 . Crustaceous. 
2. Microporella, Hincks. 
