SONNINIA REGULARIS. 395 



/3. Lobe wide- stemmed. 



Sonninia costata, 8. Buckman. See PL LXXIV, fig. 1 ; PL LXXV, figs. 1, 2, 



and page 338. 



In Sonn. scalpta and Sonn. costata the lateral lobules are so divided that they 

 might almost be said to be double, and the species might almost be described as 

 possessed of four lateral lobules to L. In addition to the septation, Sonn. scalpta 

 is distinguished from Sonn. costata by the much larger umbilicus and the smaller, 

 more numerous costse, in some places as 4 to 3 ; but the reduction in the figure of 

 Sonn. costata may perhaps mislead in these points. 



B. Lateral lobules of L fairly developed. 

 a. Lateral lobules remain nearly isometric. 



Fig. 33. — Outline of L of Sonn. parvicostata. 



Sonninia eegularis, S. Buckman. Plate XCVI, figs. 3 — 5. 



1892. Sonninia marginata, S. Buchman. This Monograph, Plate LXIV 



only (?)>. 



Discoidal, compressed, hollow-carinate. Whorls ornamented with spinicostae, 

 with costas and spinicostae 2 or 3 to 1, and then with close-set, direct, slightly 

 reclining costae, inclined but obscure ventrally. Ventral area arched, divided by a 

 well-defined, somewhat massive hollow carina. Inner margin conspicuous, broad, 

 nearly flat, nearly upright. Inclusion one-third. Umbilicus concentric, regularly 

 graduate, inner whorls spinous, regular spinous stage until the shell-diameter is 

 about 40 mm., irregular to about 70 mm. Suture-line with a fairly symmetrical 

 L, the terminal lobule practically axial, equicellate, isosceloid ; the lateral lobules 

 nearly isometric, opposite ; an accessory lobule on each side of the stem, above the 

 usual lateral lobules ; the inferior lateral lobe with two lateral lobules each side. 



1 It is requested that the explanation of the plate be altered in accordance. 



