SONNINIA RENOVATA. 433 



o. The outer lobule of L non-partite or feebly bipartite. 



Sonninia kenovata, S. Buckman. Plate XCIII, figs. 1 — 6. 



Discoidal, compressed, carinate. Whorls ornamented with ribs and spines 

 to 35 mm. diameter, the regular tuberculate stage ; then, to about 80 mm. diameter, 

 an irregular tuberculate stage with rather small reclining ribs and small spines 

 somewhat wide apart ; later to about 125 mm., a plain costate stage, the ribs of 

 small size, somewhat unequal and slightly reclining ; then a renewed tuberculate 

 stage, the ribs becoming larger and more distant with age, and nearly every one 

 drawn up in the middle into an elongate knob. Ventral area arched, divided by 

 a small presumably hollow carina. Inner margin fairly defined, steeply sloping, 

 convex. Inclusion about one-fourth. Umbilicus tending to become more excentric 

 in correlation with the renewed progressive stage — the inclusion being greater in 

 youth. Whorl-section elliptical. Suture-line with long and complex lobes ; L 

 being slightly asymmetrical, the terminal lobule anisosceloid and intra-axial — the 

 outer lobule in the adult being divided into two small portions more distinctly 

 than in the young. 



This is a most extraordinary species. When adult it is entirely unlike any- 

 thing else that has been figured. The only species with something of the same 

 character is Sonn. revirescens ; but that form is not really tuberculate, and has 

 altogether different proportions. In youth, before the noticeable secondary 

 tuberculate stage is developed, the species is very similar to the young of Sonn. 

 marginata or Sonn. dominans, — in fact, there is a noticeable agreement with the 

 specimen figured in PI. LXVII, figs. 3 — 5, which was regarded as intermediate 

 between those species. In the adult stage, however, there is no similitude with 

 either dominans or marginata ; for this strong secondary tuberculate stage which 

 makes the fossil so remarkable is not seen in either of those forms. 



From the length and characters of its lobes Sonn. renovata would appear to be a 

 lateral development of the loeuples-stock, derivable from that species. The septa- 

 tion of young Sonn. renovata agrees very particularly with that of Sonn. locuples a. 

 In the adult the lobes appear to undergo a certain amount of deterioration in pro- 

 portion to the size of the whorl — there is a tendency to shorten, and also to spread 

 somewhat laterally, as shown by the outer lobule. 1 These matters are of importance 

 in connection with certain species from beds superior to the Concavum-zone, — species 

 which possess an ornamentation similar to that of renovata, and a period of whose 

 ontogeny seems to be explained by the various developments shown in renovata. 



1 The inner lobule is not well preserved. 



55 



