﻿56 MR. F. W. O. RYMER JONES ON SOME JAVAN DEEP-SEA LAGEN^ 



or are separate, and three or four in number (figs. 40, 41), in some of which varieties 

 the lateral shell-wall is also ornamented with a few irregularly disposed trenchant costse 



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(fig. 40). This marginal keel is sometimes strengthened by a scries of sharp straight 



spines, which project into it from the periphery of the shell (fig. 42). In fig. 43, 



however, these spines are somewhat modified, and assume a flat triangular shape 

 resembling a circlet of shark's teeth. 



The foramina, as a rule, pass directly from within to the exterior, and are scattered 

 broadcast over the whole surface. But even this is found to have its exceptions; for in fig. 28 

 they occupy only the margin of the. shell, crowding together round it in a broad band. 



The shell-walls are for the most part smooth, glassy, and finely foraminated, not 

 unfrequently becoming considerably coarser. 



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These compressed forms vary greatly in their degree of compression, some being so 

 little flattened that, were it not for the marginal border, it would undoubtedly be more 

 appropriate to place them amongst the typical. Z. vulgaris, especially as this marginal 

 fihn is seen to be in a very incipient state in many of the forms here depicted. It seems 

 undesirable, however, to separate these less compressed and keeled forms from the true 

 margined^ ; for the shell delineated in fig. 28 is evidently a form of the L. {Eiitosolenk) 



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marginata mentioned by Messrs. Parker and Eupert Jones (Monogr. p. 349), and has 

 the circumambient layer of shell-deposit still undeveloped round the sides and base. 

 So completely do these forms pass into each other throusrh numberless intermediate 



o 



^ 



gradations^ that any classification of them similar to the present must necessarily be 

 artificial— though, for the purpose of identification, it is useful thus to create, as it were, 

 several nuclei around which each company can be congregated. 



A few of these marginate organisms have their exterior covered with more or less 

 blunted knobs, which are dispersed over the whole surface, and form an intermediate . 

 link with the Aspek^ of Prof.' Eeuss. 



^ Among these sheUs the marginal keel is found in every stage of development, some- 

 time's making its appearance at each side of the neck or extending with a greater or less 

 development round the periphery. 



The example delineated in fig. 27 is very cylindrical, and " squared" at the two ends, 

 the keel bemg confined to the base, and appearing unusually thickened, while the sheU 

 is destitute of either external or internal tube. 



The orifice is provided with a circlet of tooth-like processes similar to those of the 

 entoso lenian varieties figured by Prof. Eeuss (Monogr. taf. i. figs. 1-12) ; but this 

 characteristic seems to be rare in the forms from this sounding, as it is the only example 

 I have noticed m which it &' 



It is not uncommon to find among these structures examples in which the periphery 

 i^s turnished with two supplemental ribs, which become incorporated in the shell-wall. 



solwW ''"^^ '"" 7^'"^ ^^' '' *^^ '^'^ ^^^y considerably in contour, sometimes being 



xZt wTrf '"^ f-^-^-l^-ian, whHe the same L observable on ectosolenian 



7lt^, S21) ' resemblance to that figured by Prof. WiUiamson (Monogr. 



%. 28 is a somewhat flattened form, gently rounded at the base. The external tube 



occurs. 



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