148 BALANIDiE. 



ones being, as in Coronula, filled with cement. In one 

 case I counted on each trunk twenty-five glands, besides 

 some smaller obscure ones close to the centre. 



In PL 28, fig. 4 b, I have given a drawing of two of the 

 cement glands : the cement-trunk (//) is smooth and ap- 

 parently cylindrical : it becomes enlarged (at g) before en- 

 tering the gland : it seems even to be prolonged across the 

 gland under the form of a narrow bar (not represented), 

 which apparently serves to keep the two ends of the trunk, 

 on the two sides of the gland, in their proper relative places 

 and distances. The gland itself is an elongated bag (/i), 

 which properly lies exactly over the enlarged portion {g) of 

 the trunk, but in the drawing has been purposely dis- 

 placed : it gives rise, in the later-formed glands, to a sort 

 of neck (see the upper gland), which is either so long as to 

 deserve rather to be called a duct and which soon bifur- 

 cates, or is quite short (see the lower gland) and gives rise to 

 two separate ducts. On the opposite side of these glands, 

 there is a spur (m), of greater or shorter length, which is 

 evidently a rudimentary duct, for in the younger glands it 

 existed as a perfect duct. Moreover, the first-mentioned 

 duct often gives off branches (f) 3 having an exactly similar 

 appearance with the spur (m). The membrane of which the 

 cement-trunk (/), with the enlargements (y), is composed, 

 is smooth, but that of the glands and of all the ducts, presents 

 a very peculiar appearance, which at first would be called 

 scaled, but more properly perhaps notched, — each notch 

 being apparently formed by a line of thickened membrane, 

 extending obliquely round only a short portion of the tube, 

 and indenting it. The ducts, which I measured, were be- 

 tween g^eth and gfeths of an inch in diameter. 



In fig. 4 a, I have given a drawing of the two chains of 

 glands, but with only those ducts figured which proceeded 

 from the last-formed pair of glands. The specimen here 

 drawn was old j and it is rare to find the structure of the 

 ducts so simple. From both glands* a neck or thick duct 

 arises, which soon bifurcates ; one branch runs direct into 



* It should be observed that fig. 4 b ought to have been drawn with its 

 present upper end downwards, to make it correspond in position with fig. 4 a. 



