GENUS PENEEOPLIS: OKGANIZATION AND AFFINITIES. 7 



its body, this principal band being apparently regarded by him as an intestinal canal, by 

 which he supposed all the segments to be connected together. Professor EHRENBERG'S 

 figure represents a marking-out of spherules in the midst of the otherwise homogeneous 

 substance of the body, closely corresponding to those which I have described in the 

 animal of Orbitolites (^[ 43); and it also shows the skeletons of various Diatomacese 

 imbedded in the substance of the four outer segments, as I have myself found them in 

 Orbitolites (^[ 34). Consequently I can have no hesitation in the belief that the general 

 structure and mode of life of these two forms are analogous ; and that there does not 

 exist in Peneroplis, any more than in Orbitolites, that hypothetical organization which 

 Professor EHRENBERG has attributed to both. 



129. Monstrosity. The only example of monstrosity which I kave met with in this 

 type, is obviously analogous to the " monstrosities by excess " which I have described as 

 not unfrequent in Orbitolites; consisting (at least apparently) in the formation of a 

 secondary body by outgrowth or gemmation from the first. This secondary body does 

 not seem, however, to have its origin in the primordial segment, to which similar out- 

 growths may always be traced in Orbitolites (^[ 62). 



130. Affinities. As regards its general organization and plan of growth, it seems 

 clear that Peneroplis bears a very near approximation to that form of Orbiculina in 

 which the later increase takes place like the earlier upon the spiral type (^[ 87), and in 

 which there is but a single plane of chambers with a single row of marginal pores (^[ 90): 

 the only essential difference, in fact, consisting in this, that each successive increment is 

 formed in the case of Peneroplis by a continuous segment of sarcode, occupying an undi- 

 vided chamber of the shell ; whilst in the case of Orbiculina each segment is subdivided 

 into sub-segments strung like the beads of a necklace on a continuous stolon of sarcode, 

 the chamber being correspondingly subdivided by transverse partitions having a con- 

 tinuous passage through all. The very close alliance of the two forms is shown by the 

 fact, that specimens are occasionally to be met with in collections of Orbiculince, which, 

 while presenting the general physiognomy of that genus, exhibit the deficiency of trans- 

 verse partitions which is the distinguishing character of Peneroplis ; so as to render it 

 uncertain whether such specimens should be considered as Orbiculince in which (as 

 certainly happens occasionally in Orbitolites, ^[61) the usual partitions are deficient, or 

 whether they truly belong to Peneroplis, their resemblance to Orbiculina being super- 

 ficial only, and their presence among specimens of that genus merely accidental. In 

 either case it is obvious that the affinity between these two types is very close ; and in 

 fact young Orbiculince frequently present such a strong external resemblance to Pene- 

 roplis, that their true nature cannot be determined without such an examination of their 

 internal structure as will serve to disclose the transverse partitioning of their chambers. 

 It may be fairly inquired whether the peculiar striation of the surface of Peneroplis, 

 which so strongly suggests the idea of internal partitioning as to have led MONTFORT to 

 assert its existence, is not really a rudiment of that structure. 



131. Varieties. The relationship just indicated being borne in mind, it will scarcely 



