174 PROCEEDINGS OF THE ACADEMY OF [Jan., 



is completely enveloped in a growth of sponge which forms a spherical 

 mass fitting the lumen of the tube. 



Suruga Bay, 3.707, 63-75 fms.; 3.740, 65 fms. 

 Pomatoceros auritubis sp. nov. (PI. XII, figs. 33-37; PI. XI, fig. 20.) 



This species is known only from a single specimen without tube which 

 measures IS. 5 mm. in total length, of which the gills are 6 mm., the 

 operculum nearly 7 mm., and the very short thorax, without the collar, 

 2.5 mm. The branchiae have 26 radioles on each side, and each half 

 is rolled inward in a somewhat scroll-hke fashion clorsally and ven- 

 trally. The radioles are somewhat thick and are terminated by a short 

 filament free from barbs, the basal ones of which are about ^ the length 

 of the radioles, A tolerably well-developed web connects the basal f 

 of the radioles. 



The operculum (figs. 33, 34, 35) is developed from the dorsalmost 

 left radiole. Its stalk is broad and flat with prominent lateral wings 

 extending its entire length and increasing in wddth to the distal end, 

 where they terminate in narrow, pointed processes embracing the sides 

 of the opercular body. The stalk is attached excentrically to the dor- 

 sal side of the body of the operculum, which is bent strongly ventrad. 

 The body is hemispherical with somewhat flaring margins, and bears 

 by a short thick stalk on its distal face a membranous circular concave 

 plate with broad, thin, flaring margins, and a low, slightly rounded 

 central eminence. There are no spines, but two slight marks may be 

 the scars of attachment of a pair. The free margins of the disk are 

 chitinoid, l^ut there is but little indication of calcareous infiltration, 

 the body of the operculum having about the consistency of a rather 

 soft cartilage. 



The collar is high and prominent, about equalling the length of the 

 first two somites. Laterally it begins at the level of the first setse tufts 

 in a pair of lobes which are much overlapped by the dorsal membrane. 

 Its margin is much folded and serrated, finely on the dorsal, coarsely 

 on the ventral part, and in the median ventral region is produced for- 

 ward as a slender lanceolate lobe, but is nowhere deeply incised. The 

 thoracic membrane is low posteriorly, with a very delicate ventral fold, 

 but becomes high anteriorly wdth the dorso-anterior angle thrown 

 into a tuft of folds and overlapping the lateral collar lobes. 



The anterior pair of thoracic setse tufts are widely separated from the 

 others, embedded in the thoracic membrane and project forward. 

 Succeeding setigerous and uncinigerous tori of the thoracic region are 

 at first placed at a high level, but sink lower and lower until on the 

 last thoracic somite the latter are entirelv on the ventral side aiid much 



