410 INFERIOR OOLITE AMMONITES. 



B. The lobes are narrow-stemmed. 



o. The lateral lobules decidedly anisometric. 



1. The outer lobule about as large as the terminal lobule. 



v 



Fig. 40. — Outline of L of Sonn. dominica. 



Sonninia dominica, 8. Buckman. Plate CIII, fig. 14. 



1892. Sonninia dominans, var. y. This Monograph, PI. LX1X, 1 p. 323, pars. 



This species has already been figured in side view, outline of whorl-section, and 

 suture-line ; but the last has not come out very well in the printing of the plate, 

 and accordingly it has been advisable to give another figure. This is furnished in 

 PI. CIII, fig. 14 ; and by removal of test additional details have been obtained. 



The suture-line allows of the following description : — Lobes fairly long, L asym- 

 metrical, the terminal lobule very intra-axial, anisosceloid, inequicellate, the lateral 

 lobules very anisometric, the outer being about as large as the terminal lobule. 



From Sonninia dominans type (PL LXVI) this form differs by being more spinous, 

 more costate, and having a larger and more concentric umbilicus. Its suture- 

 line has a more developed outer lobule to the superior lateral lobe, making this lobe 

 decidedly asymmetrical, and the lateral lobules are very decidedly anisometric by 

 reason of excessive development of the outer one. The difference in ornament and 

 proportion, coupled with a difference in septation, makes another name a necessity. 



From Sonn. submarginata (pp. 329 and 406) this species differs in septation. 

 It is also thicker, less umbilicate, more spinous in the umbilicus, rather more strongly 

 and more regularly costate. 



Sonninia multicostata, 8. Buckman. Plate LXXXVI, figs. 1 — 3. 



Discoidal, compressed, carinate. Whorls ornamented in the brephic stage with 

 a few very rudimentary irregular spines, which soon yield to direct, nearly upright, 

 not very conspicuous, somewhat numerous ribs. Ventral area, in the neanic 



1 The reader is requested to alter the explanation of this plate accordingly. 



