﻿MR, F. W. O. RYMER JONES ON SOME 



LAGENvE. 55 



Lagena vulgaris, Wmiamson, var. sulcata, Walker & Jacob. (Pigs. 25, 26.) 



This variety, which has heen chosen hy Messrs. Parker and Rnpert'^Jones as the typical 

 form of Lagena, passes through every modification of contour from the subglohular to 

 the flask-shaped or more or less elongated structures, the external neck also bein- often 

 absent, or, when present, of very variable length, as also is the internal tube" The 

 external waUs are furnished with a variable number of thick londtudinal ribs which 



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nterruptcd, oblique spiral (fig. 2(1) 



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often.blunt or rounded (fig. 25), passing from the base to the neck, which is some 

 times left smooth. Not unfrequently these ribs take a somewhat spii'al direction, as h 

 seen in the flask-shaped form depicted by Messrs. Parker and Rupert Jones (Trans! Roy 

 Soc. vol. civ. pt. i. 1865, pi. xiii. fig. 24), and sometimes, chan^ini? their character on tli 

 external neck, wind round it in an 



encircle it with a number of transverse parallel rings. This character is also obscrvabl 

 on varieties of L. striata (fig. 18), and is seen in great perfection on a recent form of 

 L. Uspida, Eeuss (fig. 50). Messrs. Parker and Rupert Jones have unitrd the 

 L. striata, L, interruj^ta, and Entosolenia costata of Prof. Williamson with this sulcatc 

 variety, to which ought to be added the L. filicosta, L. mucronulata, and L. Villarfh'hiHinu, 

 L. Isabella, with its variety L. raricosta, D'Orb., of Rcuss (Monogr. taf. iv 

 figs. 50-56). 



• These sulcate forms appear to be of rare occurrence at this depth (1080 fathoms), the 

 only entire specimen I have met with being that delineated in fig. 25 ; there are, 

 however, a few fragments of stronger and better-developed examples (fig. 26). 



The form of which fig. 25 is a representation has the ribs very blunt and rounded, 

 some projecting slightly from the base, and extending in more or less interruj)ted and 

 wavy lines to the orifice, which is wide in diameter and lipped. 



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Lagena vulgaris, Williamson, var. marginata, Montagu. (Figs. 27-32.) 



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Shell compressed, subglohular, lenticular, pyriforra, or flask-shaped, passing througli 

 very diverse forms, from that of a compressed sphere to that of an elongated flask. 

 This group constitutes the Compress^ of Prof. Reuss, and is one of the most varied of 

 aU the Lagence, The base is most generally widely rounded, though occasionally some- 

 what apiculate. The anterior is furnished with a more or less elongated neck-tube, 

 which in some of the entosolenian forms is often absent. The mode in which this 

 external tube is " set on " is subject to great modification, gently tapering in some from 

 the flask-wall, while in others it is inserted very abruptly. The shape of the orifice is 

 likewise inconstant, sometimes being circular, while in some of the entosolenian forms 

 it is more or less compressed. The periphery of the shell is encircled by a wide thiu 

 marginal keel of transparent shell-substance, which varies ^catly in dificrcnt indi- 

 viduals, sometimes being hardly apparent, while in others it is very large. In some 

 forms this thin ridge becomes greatly thickened, appearing more rib-like (figs. 34, 85), 

 and gives rise to sharp spikes towards the base ; while in other structures the pnriphery 



becomes bluntly angular (Williamson, Monogr. pi. i. figs. 19-21), and is supplemented 

 by a smaller ridge on each side of it. In many forms these marginal outgrowths aru 

 very wide, and double, united so as to form one, like the membranes of a leaf (figs. 38, 39), 



