LUDW1GIA. 101 



difference remains to be noticed, but whether this be constant or otherwise I 

 cannot say, namely, the suture-line (Plate A, fig. 26). This differs in having a 

 longer superior lateral lobe, and a fewer number of auxiliary lobes. The size of the 

 umbilicus in the larger specimens does not give any reason (such as a lessened 

 amount of room on account of the greater width of umbilicus) for the smaller number 

 of auxiliaries ; but, when we consider that in youth the specimen is evidently less 

 involute than other species of the genus, we perhaps have an explanation. This 

 evoluteness has lessened the space, and in consequence, perhaps, two of the auxiliary 

 lobes have coalesced, and then this character has been continued in the adult. 



This species occurs in the Concavum-beds of Bradford Abbas, but is rather 

 scarce. 



Plate XIX, fig. 5, represents the side view of a nicely preserved specimen with 

 all its test present except just at the top left-hand corner, where it is broken away, 

 and should have been so depicted. Fig. 6 gives a sectional view, to show the con- 

 struction of the umbilicus. Plate XX, fig. 1, shows a larger specimen, with 

 some portion of the body-chamber present. Only a thin film of test, a remnant 

 of the under-layer, covers the greater part of the specimen. Fig. 2 gives an outline 

 of the front view. The top is drawn with test on the carina ; the other parts 

 of the carina without it. Plate A, fig. 26, gives the suture-line taken from 

 another specimen. 



Hildoceratid,e (continued). 



Genus — Ludwigia, Bayle (continued). 



(See p. 16.) 1 



Since the completion of the first part of this Monograph certain causes, among 

 them the advent of fresh material, have enabled me to work out some additional 

 species belonging to the genus Ludwigia. They are especially valuable for the 

 light which they throw upon the descent and development of this genus (pp. 102, 

 131, &c.) ; and it is fortunate that I am thus able to continue the description of the 

 species of this genus at a point where it can be again introduced not unsuitably. 



1 Erase the first four lines of heading and substitute : Family — Rildoceratidw. For the reason 

 see p. 125, et seq. 



