SONNINIA MULTICOSTATA. 411 



stage, depressed, nearly flat across, and almost square to the lateral area, 

 divided by a small, well-defined, presumably hollow carina ; later, ventral area 

 obtusely fastigate, 1 subcarinate, the two sides making an angle about 140°. Inner 

 margin well marked, sloping, angle about 65°. Inclusion about one-half. Umbi- 

 licus graduate, ornamented with costse. Whorl-section suboblong. Suture-line 

 with fairly long lobes ; L asymmetrical, with intra-axial, anisosceloid, inequicellate 

 terminal lobule, and very anisometric lateral lobules. 



It will be noticed that the suture-line of this species agrees in almost every 

 particular with that of Sown, dominica. There is the same tendency to make a 

 somewhat bifid superior lateral lobe ; there is the same large outer interlobular 

 cell of L, but the inner lobule of L is more aborted, and another lobule proceeds 

 from the inside just beyond it ; further, the outer lobule is hardly so large as in 

 dominica, but the difference is not great. 



In ornamentation the agreement with Sown, dominica is such as to justify the 

 position which the suture-line suggests, namely, descendant of Sonn. dominica. 

 There is the same series of close-set regular costae ; but they are smaller, and tend 

 to be obsolete with age. There is a similar spinous stage ; but it ends earlier, and 

 is altogether less developed than in dominica. The whorl-shape is similar but 

 more compressed. In fact, the points of difference, both in ornament and sep- 

 tation, are just those which might be expected in the descendant of Sonn. 

 dominica. 



Sonninia multicostata has some likeness to S. euromphalica, S. omphalica, and 

 S. submarginata ; but its peculiar suture-line separates it from any of them. Further, 

 it is less spinous and less umbilicate than the first ; thinner, more strongly carinate, 

 and differently costate to the second ; less spinous, differently costate, and less 

 umbilicate than the third. 



Sonn. multicostata occurs in the Concavum-zone of Bradford Abbas. It is 

 depicted in PI. LXXXVI of natural size ; side view fig. 1, outline of front view 

 fig. 2, suture-line fig. 3. 



2. The outer lobule excessively exaggerated, larger than the terminal lobule. 



Fig. 41. — Outliue of L of Sonn. palmata. 



1 Fastigatus, sloping like the roof of a house. The ventral area is bevelled on each side, and in 

 section forms an inverted j^. 



