232 BULLETIN OF THE BUREAU OF FISHERIES. 



and disposed with great regularity when the nature of the substratum will permit. The area is large 

 and elliptical or elongate oval, often somewhat bridged over at the base and on the sides by a calcified 

 lamina, marginal walls high and thin, produced at the anterior angles into a pair of blunt tubercles, 

 which project forward and outward and which are rounded at the top, convex posteriorly, and hollowed 

 out on the anterior (under) side. Ovicells and avicularia absent. 



Abundant on the Sargassum drifted into Vineyard Sound from the Gulf Stream, and in the drift 

 on the outer shores of No Mans Land, Marthas Vineyard, and Nantucket Islands. The only bryozoan 

 I have noted on the "gulfweed " and never taken in this region except on this alga. It is distributed 

 world-wide in the tropical and temperate oceans on Sargassum. 



Family CR1BRIUNIDJE Hincks, 1880. 

 Genus CRIBRILINA Gray, 1848. 



This genus includes all the members of the family occurring within our region. The arrangement 

 of the pores, and especially the development of the calcareous front wall of the zooecium indicates the 

 origin of this wall by the fusion of spines and shows a relation to Alembranipora through some connecting 

 stage such as we have in the genus Membranipordla. The posterior lip of the orifice, as well as the rib 

 over the aperture of the ovicell, may often show their development from spines even in the adult. 



KEY TO SPECIES. 



Pores disposed in transverse lines or irregularly placed; a small pointed avicularium usually situated 

 on either side of the orifice; ooecium large punctata. 



Rows of pores more or less radiating, especially on the posterior portion; avicularium wanting; ooecia 

 very small and inconspicuous annulata. 



Cribrilina punctata (Hassall). [PI. xxiv, fig. 41, 413, 4ib.] 



Hassall 1842, p. 368 (Lepralia punctata'). 



Dawson 1859, p. 256 (Lepralia punctata). 



Verrill and Smith 1874, p. 713 (Escharipora punctata'). 



Yerrill iS75b, p. 41 and 18790, p. 29 (Cribrilina puncturata). 



"\\~hiteaves 1901, p. 97. 



Cornish 1907, p. 77. 



Zoarium encrusting shells and occasionally pebbles. Zooecia small, subcylindrical, perforated 

 more or less irregularly by a variable number of large irregular openings (sometimes in old colonies 

 these may become almost closed), orifice somewhat semicircular, a small mucro in the middle of the 

 lower lip, which may become very strong with age and which is often bifid and may obscure consid- 

 erably the shape of the orifice; four marginal spines usually present, the posterior pair the larger, and 

 in fertile cells this pair is often curved inward over the opening of the zooecium, the anterior pair in the 

 fertile cells often fused with the mouth of the ovicell. Ooecium subglobose or somewhat elongated, 

 smooth and glossy, perforated by a number of small pores. Avicularia usually two, one on either side 

 of the orifice and pointing obliquely forward and outward. 



Taken at various points in Vineyard Sound, but not common. It is found abundantly in the outer 

 waters of the region; Crab Ledge, off Sankaty Head, Great Round Shoal, and Muskeget Channel, 

 dredged in 6 to 20 fathoms. Not noted in Buzzards Bay. 

 Cribrilina annulata (Fabricius). [PI. xxiv, fig. 42, 423, 42b.] 



Fabricius 1780, p. 436 (Cellepora annulata). 



Stimpson 1853, p. 18 (Lepralia annulata). 



Packard 1857, p. 270 (Lepralia annulata). 



Verrill 18790, p. 29. 



Whiteaves 1874, p. n (Escharipora annulata), 1901, p. 98. 



Cornish 1907, p. 77. 



Zoarium encrusting on stones and shells, forming small rounded colonies of a reddish or brownish 

 color, " pulcherrima et perfectissima haec omnium -cisarum" (Fabricius). Zooecia considerably coarser 



