SONNINIA. 439 



more isometric, while in Sonn. alternata the terminal lobule is extremely anisos- 

 celoid, the lateral lobules are very anisometric, and anything but opposite ; also 

 the lobes of the suture-line are very much shorter. 



" A variety of Sonninia renovata " is perhaps a sufficiently correct designation 

 for this fossil for the present. 



Sonninia, sp. 



1892. Sonninia simplex. This Monograph, Plate LXX, fig. 4 only (suture-line). 



This fossil was described as Sonn. simplex (page 326), and it bears very close 

 resemblance to the type. Its suture-line, however, does not agree with that of 

 the type, which has been since worked out, and is depicted on PI. CIII, fig. 11. 

 In this respect it has more to do with Sonn. dominica and Sonn. multicostata. If it 

 be a development of those forms, its external likeness to Sonn. simplex is truly extra- 

 ordinary. 



Sonninia, sp. Plate LXXII, figs. 1, 2. 



This form has considerable external resemblance to Sonn. substriata (page 330), 

 but is more costate and more carinate. It may be placed in proximity to that 

 species until septal evidence to the contrary be forthcoming. 



Sonninia, sp. Plate LXXIX, figs. 7, 8 (see page 349). 



The external appearance indicates alliance with Sonn. crassiformis (page 348), 

 but it is not a young form of that species. 



Sonninia, sp. Plate LXXXIX, figs. 9, 10. 



This fossil may be the young of Sonn. simplex. The rudimentary state of the 

 spinous stage, which may reasonably be considered as vestigial, is particularly 

 noticeable. The costse are shown rather too strongly in the drawing. The 



