586 



BEY. R. BOOG WATSON ON THE 



be necessary to place it in an independent section of the class. 

 To this we may assign the name of Poltzoa aspidophoea. 

 Indeed I regard Rhabdopleura as entitled to a rank at least as 

 high as that of the Ectoprocta and Endoprocta ; and the Aspi- 

 dophoea will thus constitute a third great section of the class. 



The hydroid affinity attributed to Bhabdopleura by the elder 

 Sars, and accepted by his son, is based on a misconception of 

 hydroid structure and development, as doubtless the distinguished 

 Scandinavian zoologist would, on more mature consideration, 

 have been among the first to admit*. 



MOLLUSOA OF H.M.S. ' CHALLENGER ' EXPEDITION. 



III. Trochid^, viz. the G-enera Seguenzia, Basilissa, Gaza, and 

 Bemlix. By the Eev. E. Boog Watson, B. A., E.L.S., &c. 



[Read December 5, 1878.] 



The following group of genera are of considerable interest. They 

 are nearly all from very deep water. Of the Seguenzias, two spe- 

 cies are new ; and some additional information of interest has 

 been obtained regarding the genus. Basilissa is a new genus 

 whose labial and basal sinus connect it with Seguenzia ; while 

 both genera present JBleurotomaria features hitherto unknown 

 among the Trochidse. Gaza is utterly distinct, not alone from 

 these two genera, but from any thing known in the family, in 

 which a reverted thickened lip is an entire anomaly. The genus 

 Bemlix, here proposed, is made for a new form of the Trochidae, 

 presenting an epidermis. 



Seguenzia, Jejfr. 



J. G. Jeffreys, Eeport on the Biology of the ' Valorous ' cruise, 

 Eoy. Soc. Proc. No. 173, 1876, p. 200. 



In all the species of this genus I have seen, besides the infra- 

 sutural sinus resembling that of Pleurotoma, there are two others 

 — one, which is rather sharp and slight at the carina, and another, 

 opener, on the base : between all of these the lines of growth 

 curve out strongly towards the mouth. This might probably be 

 accepted as a generic character. It is a feature very difficult to 

 trace ; but it certainly exists. In a perfect shell the mouth-edge 



* See Ray Lankester in Quart. Journ. Micr. Sci., Jan. 1874. 



