SUPPLEMENT.— LIOCERAS. xxxiii 



general characters nearest to Phymatoceras, but lacks the bisulcate periphery 

 found in the stenogyral species of that genus ; besides, the carina is small and 

 non-septate. 



3. Brodieia ? Witchelli, S. Buchnan. Plate XXIII, figs. 9, 10. 



1889. LuDWiorA sp., This Monogr., PI. xxiii, figs. 9, 10. 



Description. — Substeno-leptogyral, excentrumbilicate, parvinodate, 1 rursi- 

 flexicostate, parvi-nonsepti-carinate. 



Localities and Stratum. — Gloucestershire : Nailsworth (Cotteswold Sands — 

 E. Witchell, F.G.S., the figured specimen); Standish Beacon (Cotteswold Sands). 



Date of Existence. — Variabilis hemera. 



While this sheet is passing through the press, Mr. G. C. Crick, F.G.S., informs 

 me that a genus " Brodia" is already in use for fossil insects. Therefore it is 

 necessary to substitute Brodiceras for Brodieia above. 



The Genus Lioceras and opalinoid Ammonites. 



There is very considerable trouble here, and so it is necessary to make the 

 following prefatory remarks : 



Hyatt establised the genus Lioceras, and referred thereto eight species of what 

 may be called platyleptogyral, angustumbilicate, striate or subcostate Ammonites. 

 Bayle employed it as a generic designation in a somewhat similar manner, but 

 omitted therefrom the species opalinus, which he referred to Ludwigia. 



When I discussed the genus Lioceras 2 I selected from Hyatt's original series 

 three species which, as it seemed to me, possessed genetic affinity. From these 

 three species I chose opalinus to be the type of the genus. Of the remainder of 

 Hyatt's original series I placed lythensis as the type of another genus, l J srn<li>- 

 lioceras ; discoides as the type of yet a third genus, Pohjplectus ; while in a later 

 communication I gave definite restriction to the genus Harpoceras, constituting 

 falcifer as its type species : that genus would probably embrace the remainder of 

 Hyatt's origiual series. 



So far the matter is sufficiently straightforward. Opalinus is the type of 

 Lioceras, although its selection for that position was founded on more than one 

 misconception, particularly a mistake as regards the genetic affinity of the species 



1 The nodi are a little elongate in the direction of the costae. 



2 This Monogr., p. 12. 



