BRYOZOA OF WOODS HOLE REGION. 233 



than in the last species, and usually much less regular in form, the punctures arranged in rows which 

 are transverse anteriorly but toward the posterior end tend to radiate, a median ridge or carina 

 often present; orifice in the young zooecium nearly semicircular or with a small denticle on the lower 

 lip, but in the later stages the lip becomes greatly thickened, and, especially in the fertile cells, where 

 a secondary lip extends over the ovicell, the original nature of the orifice is entirely obscured; usually 

 four short spines project forward on the anterior lip, the anterior pair being smaller and somewhat diver- 

 gent. The ooecium is small, hemispherical, punctured with a few pores, and overgrown to a varying 

 degree by a secondary lip which is formed by the greatly developed and often fused posterior pair of 

 oral spines. Avicularia wanting. Not infrequently there occur fertile zooecia of smaller size than 

 usual, standing nearly erect between the ordinary zooecia. 



Rare and occurring only in the outer waters; Crab Ledge and Nantucket Shoals, 14 to 20 fathoms. 

 These records greatly extend the known southward range of the species, which has not been reported 

 south of the Bay of Fundy (Stimpson). 



Family PORINID^E d'Orbigny (pars), 1851. 

 Genus PORINA d'Orbigny, 1851. 



This genus is easily determined by the tubular character of the zooecial orifice, together with the 

 presence of an elevated rounded pore on the front wall below the orifice. 



Porina tubulosa (Norman). [PI. xxiv, fig. 43, 43a, 43b, 43C.] 



Norman 1868, p. 308 (Lepralia tubulosa). 

 Whiteaves 1901, p. 98. 



Zoarium forming small, rounded, white colonies on stones and shells. Body of zooecium recum- 

 bent, rather elongate, punctured with small pores which under a high magnification are found to be 

 stellate in appearance; orifice tubular, much extended, more or less erect, thin, often produced irregu- 

 larly at the margin, a large median pore near the lower part of the tube and surrounded by a projecting 

 ring or tubule. Ooecium small, flattened, situated low down behind the erect tube. In the develop- 

 ment of the fertile cell the tubular neck is thus seen to be of secondary formation. Avicularia absent. 



Not common, and found only in the outer waters of the region; Muskeget Channel, Crab Ledge, 

 and Nantucket Shoals; dredged in 7 to 20 fathoms. Not previously noted south of the St. Lawrence. 



Family MICROPORELLIM Hincks, 1880. 

 Genus MICROPORELLA Hincks, 1877. 



The special median pore, which distinguishes our species in this family, is not always easy to see, 

 since, in some conditions of calcification, it may be more or less hidden in front of an umbonate process. 

 A little experience is necessary also to distinguish it at once from the small avicularia which may have 

 the same position, just below the orifice, in certain other groups. The semicircular form of the zooecial 

 orifice, without any prominence on the posterior, straight, border, is also a good character. 



KEY TO SPECIES, 



Median pore below orifice sublunate, or more or less semicircular, with a toothed projection extending 



into the opening from the anterior border . .ciliata. 



Median pore circular, with spinules projecting from all sides toward the center var. stellala. 



Microporella ciliata (Pallas). [PI. xxiv, fig. 44, 443, 44b, 44C, pi. xxx, fig. 90.] 



Pallas 1766, p. 38 (Eschara ciliata). 

 Packard 1867, 270 {Lepralia ciliata). 

 Verrill 18790, p. 29 (Porellina ciliata). 

 Whiteaves 1901, p. 98. 



26195 12 3 



