BRYOZOA OF WOODS HOLE REGION. 231 



Membranipora flemingii Busk. [PI. xxm, fig. 38.] 



Busk 1854, p. 58. 



Verrill 18790, p. 29 (Mollia flemingii). 



Verrill 1885, p. 530. 



Zoarium encrusting shells, stones and occasionally algae, the outline usually irregular and the 

 cells often crowded and distorted. Zooecia moderately large, iisually irregular in outline and in disposi- 

 tion, sometimes so crowded as to be greatly distorted; area expanded below and much constricted at 

 the anterior third, partially bridged over by a calcareous lamina posteriorly and laterally, leaving a 

 somewhat trifoliate membranous area; margin high, granular, with four to six spines, one of which 

 usually attains a much larger size than the others (I have seen no specimens from this region with the 

 flattened scimitar-like spine described by Hincks; the large spine is stout, round and nearly erect). 

 Ovicell rounded, sometimes partially immersed, bearing a raised rib which incloses a somewhat quad- 

 rangular space on the front. Avicularia placed one on either side of the ovicell at the base of the 

 zooecium, with the rather elongate mandible turned forward and sometimes a little outward, but in case 

 o ooecium is present there is a single avicularium with its mandible reversed to point backward (often 

 obliquely or even transversely placed). The avicularia are thus similar to those of aurica in arrangements 

 and in the influence of the ooecium, but they are not so regular in position and the mandible is more 

 pointed. 



Rather widely distributed but not common, taken in Vineyard Sound, Muskeget Channel, Crab 

 Ledge, and off Sankaty Head, dredged in 7 to 20 fathoms. A common European species, recorded 

 from Eastern Greenland, and Verrill has noted its occurrence off Nova Scotia in 234 fathoms. 



Membranipora tenuis Desor. [PI. xxin, fig. 39, pi. xxx, fig. 87.] 



Desor 1848, p. 66. 



Verrill and Smith 1874, p. 712. 



Desor 's description of this species is very inadequate, but there is no other species to which, under 

 the circumstarrces, he could have referred. I have redredged his type locality and found the species 

 very abundant there. "Cells lobate, more elongated than in M. pilosa Pallas, with a plain margin of 

 a pale pink color. Abundant in Muskeget Channel from 3 to 5 fathoms." (Desor, 1. c.). 



Verrill (1. c.) adds to the above: "Common on pebbles, often covering their whole surface with a 

 delicate, lace-like incrustation, made up of very small, crowded, oval or oblong cells, which have the 

 inner part of the front partly closed over, but with an irregular, mostly three-lobed aperture toward the 

 outer end, which is bordered by small, irregular spinules." 



I may state, in addition, that the zooecia are not unusually small for a Membranipora, as one might 

 infer from Verrill 's description, but are of moderate size. The raised margin is high and finely tuber- 

 cular on its inner side, and the calcareous lamina is finely punctate; rounded knobs, apparently pro- 

 jecting from the spaces in the angles between the zooecia, are frequently present. Considerable varia- 

 tion is shown in the extent and shape of the calcified lamina, and in the size and shape of the knobs. 



Membranipora danica Levinsen (1894, p. 53-54, text-fig, i and 2) must be very closely related to, 

 if not identical with tenuis, but without the examination of specimens I hesitate to place it positively 

 in the synonymy. 



Muskeget Channel (Desor) ; Vineyard Sound (Verrill). Common and widely distributed throughout 

 the region. Most common on the pebbly and shelly bottoms of Vineyard Sound. Muskeget Channel, 

 and Great Round Shoal; rather scarce in Buzzards Bay, except near shore, owing to the predominance 

 of muddy bottom and the lack of proper attachment. 



Membranipora tehuelcha (d'Orbigny). [PI. xxiv, fig. 40.] 



D'Orbigny 1839, p. 17 (Flustra tehuelcha). 



Waters 1898, p. 674-6 (synonymy of M. tuberculata Busk with this species). 



Zoarium encrusting on "gulfweed" (Sargasmm baccifcrum), appearing as a beautiful white net- 

 work against the brown stems and floats of the alga. Zooecia of moderate size, usually rather elongate, 



