25O BUSH 



Spirorbis stimpsoni Verrill 1879. pi. xxxix, fig. 38; pi. XL, fig. 



29; Pl. XLIII, figS. 2O, 21, 22. 



This species forms regularly coiled sinistral tubes with large central 

 cavity, the aperture occasionally turned upward, the surface often 

 roughened by growth lines and a small rounded median thread. 



Spirorbis pusilloides nom. nov. for Mera pusilla Saint-Joseph 1894. 

 As the pusilla of Saint- Joseph is now referred to the genus Spir- 

 orbis, and as this specific name was used by Rathke in 1836 for a form 

 from the Black Sea, S. pusilloides is proposed for Saint- Joseph's 

 species. 



Spirorbis pseudocorrugatus nom. nov. for S. corrugatus Caullery 

 and Mesnil 1897, non Montagu 1803 (see p. 248). 



Spirorbis f oraminosus Bush 1 904. 



Tubes forming a good sized dextral discoid coil, the surface orna- 

 mented with 3 carinae, the median one the most prominent, on both 

 sides of which the slightly concave surface is punctured by irregular 

 minute holes or foramina apparently caused by the erosion of the epi- 

 dermal layer ; immature forms probably having the surface crossed by 

 numerous transverse lines. The operculum, which is a brood-pouch, 

 is elongated, cylindrical, filled with eggs, the calcareous plate a simple 

 disk with flaring rim with large shield-shaped basal portion attached 

 posteriorly to a secondary calcareous disk on the end of the operculum 

 proper. Setae with simple tapered blades, those on the collar the 

 broadest and more abruptly tapered than the others. 



Spirorbis bellulus Bush 1904. 



Tube dextral, regularly coiled, with small central cavity, the surface 

 ornamented with 3, sometimes 4, unequal rounded threads, the one on 

 the summit the most prominent. The calcareous plate on the opercu- 

 lum somewhat angular, with deep upright thickened rim. Setae with 

 long slender tapered blades, those on the collar with comparatively 

 coarse serrations. 

 Spirorbis dorsatus Bush 1904. 



Tube dextral, regularly coiled, with a single high median ridge on 

 the last whorl. No animal found. 



Spirorbis argutus Bush 1904. 



Tube sinistral, forming a low discoid coil with large central cavity, 

 spreading around the base in a thin layer, the whorl rapidly enlarg- 

 ing and ornamented with one large median keel and numerous distinct 



