BRYOZOA OF WOODS HOLE REGION. 227 



6. An area on the front wall below the raised margin perforated with large pores, spines all strong, .pilosa. 

 Area below raised margin not so perforated, spines weaker, the median spine at lower edge of 



aperture stout, others occasionally absent monoslachys. 



5. Spines few, usually 2, one on either side of the apertiu-e at the upper end, ooecium usually 



with a strong suberect avicularium on its forward end unicornis. 



Spines more numerous 7. 



7. Spines usually 13 or more, bent downward over the aperture and flattened in cross section, 



directed strongly fonvard craticula. 



Spines less in number, not strongly directed forward 8. 



8. Spines usually less than 12, nearly erect and pointed, except the most anterior pair, which 



are blunt at the end and directed somewhat forward lineaia. 



Spines 4 to 6, one or two erect, the others broad and flattened and bent downward over the 



aperture, a small avicularium on either side, occasionally on one side only (sometimes 



with a large avicularium transversely placed at the base of the cell, variety armifera) . . arctica. 



3. Goecia present g. 



Goecia wanting 10. 



9. Ooecium with a strongly raised rib inclosing a somewhat triangular area aurita. 



Ooecial rib not so strongly developed, inclosing a rectangular area flemingii. 



10. Small avicularia situated on the tops of slender pedicels among the marginal spines, which are 



long, zooecial walls ver>' high cpnbcvformis. 



Avicularia wanting; spines, when present, in the form of stout tubercles 11. 



11. Calcareous lamina well developed, half closing the area, with strong teeth projecting toward 



tlie center tenuis. 



Lamina much less developed, lacking the strong teeth of the last species; in this region found 

 only on floating Sargassum of tlie Gulf Stream drift tehuelcha. 



Membranipora lacroixii (Audouin). [PI. xxii, fig. 28, 28a, 28b.] 



Audouin, 1826, p. 240 {Flustra lacroixii). 



? Packard, 1867, p. 8. 



Dawson, 1859, p. 256. 



Hincks. 1880, p. 13I. 



Waters. 1898. p. 679. 



Whiteavcs, 1901, p. 97. 



Zoarium encrusting, forming a delicate network over stones, etc. Zooecia rather small, the mem- 

 branous area large and only slightly depressed, i. e., nearly flush with the calcareous margin. The latter 

 is finely granulated on its inner border, and it is slightly raised at the anterior end of the cell in front 

 of the operculum. There are no tubercles, avicularia, or ovicells in this species, and tlie slender 

 spinules, of which 2 to 12 may be present in the species, are absent from tlie only specimen I have seen 

 from this region. A colony which was kept for several months living in a standing aquarium at New 

 Haven by Dr. L- J. Cole has the spines well developed. An excellent diagnostic character, mentioned 

 by Waters (1. c), isfound in a pair of rounded uncalcified areas near the anterior end on the underside 

 of the zooecium, with other smaller areas occasionally present, but to discover these it is necessary to 

 remove the zooecia from the substratum. 



The species has been so confused in the literature that records of its occurrence are some- 

 what doubtful. Our species is identical with that which Waters discusses under this name. Packard, 

 Hincks, and Whiteavcs have listed it for Canada, and may have been correct in so doing. 



A single large colony, several inches in diameter, encrusting a stone, was taken in the estuary of 

 the Weweantic River, at the head of Buzzards Bay, near the low-tide mark, by Dr. E. D. Congdon. 



Membranipora monostachys Busk. [PI. xxii, fig. 29, 29a, 29b, pi. xxx, fig. 87.] 



Busk. 1854. p. 61. 



Leidy, 1855, p. 9 (Escharina ttneata). 



? Verrill and Smith, 1884, p. 712 C.\/. lineata). 



