LILLIA SULCATA. 109 



certain specimens of this genus very kindly sent to me by Dr. Canavari from the 

 Upper Lias of Italy) that Ludwigia is descended from Lillia through Lillia 

 comensis or Bayani. One of the greatest differences between the two genera is 

 the narrow siphonal lobe of the latter genus compared with the broad siphonal 

 lobe of the former with its divergent terminal points. The other differences, such 

 as gradual disappearance of furrows, the projection and recurving of the ribs on 

 the lateral area, and the development of more auxiliary lobes, are nothing more 

 than the changes which we ought to expect to find during the gradual evolution 

 of these genera from Arietites. Similar changes must have taken place among the 

 ancestors of the genera Harpoceras, Lioceras, &c, to evolve them from Arietites 

 (see p. 133, et seq.). 



One species which I have to describe, and which belongs apparently to this 

 genus, is rather interesting and peculiar. The reason for doubting whether this 

 be its correct position is that I have seen but a portion of the suture-line, and that 

 the species occurs so very much later than any other species of the genus. Three 

 or four life-zones, which have hitherto yielded, so far as I am aware, no species of 

 the genus Lillia, intervene to isolate Lillia sulcata from those species which we 

 meet with in the Upper Lias. 



This genus contains the following already-named species, none of which can yet, 

 to my knowledge, be recorded as British : Am. comensis, 1 von Buch ; Am. Bayani, 

 Dumortier ; Am. Escheri, von Hauer ; Am. erbaensis, von Hauer ; Am. rheumatisans, 

 Dumortier; and probably Am. Lilli, von Hauer, and Am. tirolensis, von Hauer. 

 The last four species are part of the series to which Dumortier gave the name 

 " Podagrosi." 



The specimen figured by Bayle as Lillia Lilli seems to be rather different to 

 von Hauer' s species Am. Lilli. 



Lillia sulcata, 8. Buckman. Plate XXII, figs. 32, 33; Plate XXIII, fig. 1. 



Discoidal, slightly compressed, carinate, furrowed ventrally; whorls quad- 

 rate, with their sides very slightly convex, ornamented on the inner area with 

 small knobs at irregular intervals, from which, generally in pairs, and from 

 between which singly, rather coarse rounded ribs spring. These run rather 

 straight on the lateral area, bend slightly forward on the ventral area, and die 

 away at the furrows. The ventral area is rather flat, carries a small, solid, rather 

 sunken carina, bordered by two conspicuous furrows. The inner margin is convex 



1 Am. comensis has been quoted from different places, but, in my experience, incorrectly. 



