BRYOZOA OF WOODS HOLE REGION. 237 



points forward and outward in the usual form, though in the form reversa it points backward and outward; 

 usually at least one avicularium is present, but not infrequently they may be lacking over a large part 

 of the colony. 



The species shows an endless amount of variation in almost all the characters except the orifice, 

 which is fairly constant. The var. ansata (Johnston) with the raised border sepa/ating the zooecia is 

 commonly found in deeper water, though the ordinary form may occur alongside of it. Verrill's 

 Hippothoa reversa was based on the reversed avicularium and is a pure synonym, since this condition 

 may occur in the same colony with normally placed avicularia, and all sorts of intermediate conditions 

 occur. 



One of our most abundant and characteristic species, found almost everywhere except on bottoms 

 of pure mud and sand where nothing exists to afford attachment. Not taken in the outermost dredgings 

 at Crab Ledge and off No Mans Land. Taken from low water to 19 fathoms. 



Schizoporella biaperta (Michelin). [PI. xxv, fig. 49, 4ga, 4gb.] 



Michelin 1841-42, p. 330 (Eschara biaperla). 



Verrill iSysb, p. 41 (Hippothoa biaperta); i87gb, p. 193, and 18790, p. 30 (Escharina biaperta). 



Whiteaves 1901, p. 100. 



Zoarium incrusting or rising into free expansions. On stones and shells it forms smooth flat colonies 

 with a more or less regular outline, on algae and hydroid or other stems usually forming shelf-like expan- 

 sions, often of great beauty; color in life varying from white or translucent to bright pink or red. Zooecia 

 ovate or hexagonal, more or less gibbous, punctured (at least in the younger stages) by small pores; 

 surface smooth and glossy, becoming rough and dull with advancing calcification; separated by a 

 raised border which may be obscured by later calcification; orifice subcircular, the posterior border 

 straight with a rather wide sinus, peristome not raised except in the fertile cells, when it may extend 

 upon the ovicell; no oral spines. Ooecia rounded in outline, often considerably impressed, upper 

 surface flattened, with radiating lines, the flattened area surrounded by a thick border rising from the 

 base. Avicularia one or two with rounded or oval mandible, situated on a rounded prominence at the 

 side of and facing toward the orifice. The mamillate processes bearing large pointed avicularia, which 

 Hincks states are common, seem to be very rare in this region. 



A large amount of variation is exhibited, but most of it is traceable to the degree of calcification. 

 The characters of the ooecium and of the oral avicularia afford the best criteria for identification. 



An abundant species, well distributed throughout the region, and dredged in 3 to 20 fathoms. Buz- 

 zards Bay, Vineyard Sound, Muskeget Channel, Great Round Shoal, Crab Ledge, No Mans Land (drift). 



Schizoporella auriculata (Hassall). [PI. xxv, fig. 50, soa.] 



Hassall 1842, p. 411 (Lepralia auriculata). 



Packard 1867, p. 408 (Lepralia globifera). 



Verrill 18753, p. 414 (Escharella auriculata); i87gb, p. 192-3 (Smitlia globifera); and 18790, p. 30 (Smitlia auriculata and globifera). 



Whiteaves 1901, pp. 100 and 106 (as Schizoporella auriculata and Smitlia globifera). 



Zoarium encrusting, often quite irregular, on stones and shells, and occasionally on hydroid stems, 

 in which case it may rise free for a short distance, varying from colorless to reddish or yellowish. Zooecia 

 usually quadrangular and disposed in linear series, with a well-developed raised border, more or less 

 punctate, with a well-defined series of large areolse around the edge of the cell next to the border; in 

 older stages of calcification the surface may become very rough and ribbed, but the marginal ureolas 

 remain distinct; orifice subcircular with a rather broad but well-defined sinus in the posterior margin. 

 Ooecia large, rounded, raised, or occasionally more or less immersed; the upper surface somewhat flat- 

 tened, punctate, often radiately striate, with a thin border surrounding the flattened area. A small 

 avicularium with a broadly rounded to somewhat pointed mandible is centrally placed just posterior 

 to the orifice, sometimes projecting forward so as to obscure the sinus and the orifice to some extent. 

 Hincks mentions a large avicularium which sometimes replaces the small one, but I have not seen 

 this in our specimens. 



