246 BUSH 



The operculum differs from that of all other species in having three 

 distinct parts, each with a similar calcareous plate. In some instances 

 the two upper parts have been torn away, leaving one plate in the 

 operculum which is filled with well-developed embryos, each with a 

 conspicuous patch or mass of white, which under pressure separates 

 into minute rods that are soluble in acid. Similar white masses 

 have been found in the embryos in the operculum of the eastern S. 

 granulatus and S. validus. Their exact significance has not been 

 satisfactorily determined. They apparently have not before been noted. 



Setae finely serrate blades, not very unlike those of S. asperatus. 



On fragments of rocks with S. variabilis. 



SPIRORBIS INVERSUS sp. nov. 



Type locality. Port Phillip, Australia. 



Isolated, minute, opaque, very lustrous, sinistral tubes, closely allied 

 in form to S. lucidus, are attached to the tips of the lower or sheltered 

 branches of a bryozoan {Menipea cirrata Lam. ?) in the Yale Uni- 

 versity Museum. 



They are remarkable for the turning downward, like a spout, of 

 the more or less elongated terminal portion, but at first form regular 

 flat coils. No definite characters could be obtained from the much- 

 dried animals. No record of such a species has thus far been found. 



SPIRORBIS TRIDENTATUS sp. nov. 



Type locality. Port Phillip, Australia. 



Associated with S. inversus on the bryozoan Menipea cirrata are 

 numerous other isolated white tubes which are carinated and dextrally 

 coiled more or less irregularly upward when mature, the margin of the 

 aperture with two deep angular incisions forming three conspicuous 

 angular teeth. 



They differ from all known forms in having the lower surface of the 

 whorls distinctly smaller than the upper surface, the sides inclined out- 

 ward forming a carinated shoulder, with the usually flattened upper 

 surface, on which is a much larger median carina ; a third defines a 

 small, deep, central cavity, but in many full-grown specimens the inner 

 one is inconspicuous or wanting. No animals were found. 



This species may prove to be either S. lamellosus Lam. or S. in- 

 cisus Morch (S. carinatus Lam. non Montagu) described by La- 

 marck in 1818, from King Island, which is south of Port Phillip. The 

 descriptions are inadequate for accurate identification, and the figures 

 by Chenu have not been seen. 



