Polyzoa of the St. Lawrence. loo 



differs remarkably in appearance from the rest of tlie cell, 

 which is of a brown colour and thickly covered with pores. 

 It is smooth, dense, and of a whitish colour, showing very 

 distinctly on the dark front wall. The avicularium lies across 

 the upper part of it, innncdiately under the lower margin of 

 the orifice, slanting slightly upwards. The whole structure 

 probably represents the umbo of the normal form. Its effect 

 on the general appearance of the cell is very striking. 



The orifice in this species is wide and well arched above, 

 but below the articular denticles, which are placed more than 

 halfway down, it narrows off and terminates below in a curved 

 line. The structure of the orifice would seem to connect it 

 with the genus Schizoporella rather tiuvn Lepralia. 



Memhranipora armifera^ IJincks. (PL VIII. fig. 4.) 



Memhraniporu armifera, Hincks, " Contributions towards a General 

 History of the Mariue Poljzoa," ' Annals," ser. 5, vol. vi. p. %2, pi. xi. 

 tig. 5. 



Some time since I described a species of Memhranipora from 

 the 8t. Lawrence under the above name; but it now appears 

 that the specimen was immature on which the description 

 was founded. Fortunately the occurrence of the perfect form 

 enables me to revise and complete the diagnosis. 



Zooccia ovate, quincuncial, wholly membranous in front, 

 margin rather wide, the inner border crenulate, two spines at 

 the top, on each side (or sometimes on one only) a little 

 below the upper margin an acute avicularium^ placed obliquely 

 on the top of a prominent bracket- like support, carinate in 

 front, mandible directed downward, a tall and very stout 

 articulated spine rising from the margin close to one or (occa- 

 sionally) both of the lateral avicularia, immediately below 

 the cell a large mounted avicularium. Ooecium rather large, 

 much broader than high, surface smooth and entire, a promi- 

 nent rib across it a little above the oral arch, and at the top a 

 large elongate avicularium placed obliquely and stretching 

 along one side of the cell above, mandible pointed. 



Hah. On shell and stone, and incrusting Flustra memhra- 

 naceo-truncata, Smitt. 



Commonly only one of the lateral avicularia is present, and 

 the large articulated spine takes the place of the other, hi 

 some cases both avicularia are present, each with an attendant 

 spine. When the ooecium is developed it adheres to the 

 avicularium at the base of the cell above, which appears as if 

 it were a part of it. 



This species is nearly allied to 31. unicornis, Fleming. 



