GENUS LAGKNA. 157 



name Serpida, with Lajjcna appended in brac]\ets, apparently as a sub-generic name. Tlic 

 designation Vermiculum was given to these by Montagu (lxv) ; but some subsequent writers 

 on British shells went back to the comprehensive term Scrpula .■ whilst others modified 

 Walker's Lagena into Lur/cnitla. The peculiar modification of this type which consists in the 

 introversion of the flask-shaped neck (an example of wliich had been figured by Walker) was 

 distinguished by Ehrenberg under the generic name Entosolcnia. It was not until 1839 

 that this type was noticed by M. D'Orbigny ; and he seems to have remained in entire igno- 

 rance that it had been previously described ; no allusion being made in liis latest enumeration 

 of the genera of Foraminifera (i.xxiv) to the Monograph of the genus Lcifjena published 

 some years previously Ijy Prof. Williamson (cvi), in which Walker's original generic name 

 was restored, and the question of the value of specific distinctions in this group first 

 treated (as I have already had occasion to observe, p. 9) in a truly philosophical spirit. The 

 identity of Oolina and Lagena has been noticed by Pictet (' Pak'ontologie,' tom. iv, p. 483) ; 

 who has riot, liowever, substituted the original designation for that of D'Orbigny. 



237. External Characters, and Internal Structure. — The typical Lagena is a minute 

 globose shell with a prolonged neck and terminal aperture, very much resembling a Florence 

 flask. It is frequently elongated, however, into an ovate form, and may even be pointed at 

 its posterior extremity, being at the same time so much narrowed as to become fusiform in shape. 

 In some of the slenderest forms there is a tubular aperture at each end; and such are occasionally 

 somewhat bent. Like the Entowlenin figured by Prof. Williamson (ex, fig. 32 a) these are 

 perhaps to be regarded as " double monsters." The aperture at the extremity of the neck is 

 surrounded by a thickened rim ; this is frequently notched or denticulated so as to form a set 

 of radiating fissures ; and sometimes the central portion of the aperture is filled up by a plug 

 of calcareous matter. There is a large fossil I^agena, in which the neck has secondary 

 tubular apertures arising from it laterally and almost at right angles to the main tube. 

 The surface is sometimes smooth, but is more frequently marked with elevated costa, 

 which usually spring from the centre of the posterior extremity, and extend in a meridional 

 direction towards the neck, sometimes, however, proceeding no further than the equator (ex, 

 figs. 5 — 14). These costoe vary greatly in number as well as in lengtii; when they are fewest 

 they are usually most prominent ; and when most numerous they are so closely approximated 

 as to give a fluted character to the surface. They are distinguished, moreover, from the 

 general surface, not merely by their prominence, but by their more glistening aspect ; and 

 this results from the fact that whilst the substance of which the shell generally is composed is 

 finely tubular, that of the eo-st<e is destitute of tubuli. In the strongly costated forms the 

 tubuli are generally disposed in rows parallel to the costse ; and sometimes they are limited, 

 like the costos, to the posterior portion of the shell. There is seldom in the typical LagencE 

 any considerable anastomosis of the costse, though traces of it are sometimes observable. — 

 The length of these little shells is generally between l-45th and 1-lOOth of an inch. 



238. The apertural tube or neck is sometimes prolonged internally instead of externally ; 

 and on this introversion the genus Entosolenia has been founded. The propriety of this dis- 

 tinction, however, was questioned in the first instance by Prof. Williamson (cvi), and still 

 more strongly by Messrs. Parker and Rupert Jones (lxxxi), who have finally (lxxvi) come 



