MOLLUSCA or THE ' CHALLENGER ' EXPEDITION. 593 



narrowed by the reverted pillar-lip and by the corresponding 

 ridge which twines spirally round the pit-wall. Below this ridge 

 is a very strongly marked furrow, which corresponds to the 

 pillar-tooth. H. 0-14. B. O'lS ; least breadth 0-13. Last 

 whorl 0-06. Mouth, height 0-05, breadth 0-06. 

 This species most resembles S. cmnnata, Jeffr., but is narrower, 

 sharper, and the last whorl is larger : the suture is angulately im- 

 pressed instead of being faintly linear ; the spiral threads are 

 stronger, and are picked out with tubercles ; the base is more 

 equably curved, the spirals on it are stronger : the umbilicus is 

 smaller, and is more strongly defined, not only by the stronger 

 carina, but by the extracarinal furrow\ The pillar-tooth comes 

 in higher up than in that species. 



Basilissa, W., gen. nov. (fiarriXiacTa, queen,) 

 Testa conica, cariuata, umbilicata, margaritacea, anfractu ultimo superne 

 sinuate; columella recta, parum obliqua, tenuis, superne excavata, in- 

 ferne vix dentata, ad basin autem valde angulata ; apertura rhom- 

 boidea, labiis nee conniventibus nee callo palatali junctis. 



The special feature of this genus is the sinus in the outer lip 

 near its junction with the body. In the presence of such a sinus 

 it resembles Seguenzia, Jeffr., but differs from that genus in this, 

 that Basilissa has a wide, open, shallow, not a deep-cleft sinus, is 

 brilliantly nacreous, and lacks the sharp tooth on the pillar with 

 the strongly marked sinus above and below it. It also wants the 

 carinal sinus which all the species of Seguenzia I have examined 

 present ; and the basal sinus can scarcely be said to exist, though 

 on the base the lines of growth change their direction markedly 

 below the carina. 



In form, in sculpture, and in its sinus this genus recalls M'Coy's 

 genus FlatyscJiisma, a Carboniferous fossil; but that belongs to 

 the Solariidae, and is distinguishable at once by the absence of the 

 mother-of-pearl structure of shell, by its rounded mouth, and by 

 its short pillar. 



List of Species. 



1. Basilissa lampra, "W. 4. B. alta, W. 



2. B. simplex, W. 5. B. superba, W. 



3. B. munda, 'W. 6. B. costulata, W. 



1. Basilissa lampba, W. (AayuTrpos, shining.} 

 St. 246. July 2, 1875. Lat. 36^ 10' N., long. 178° 0' E. Mid 

 Pacific, east of Japan. 2050 fms. Grey ooze. 1 specimen. 



