136 



and again divided into two parts by a ridge running from the apex downwards. At a little distance 

 from the apex this ridge begins to show traces of teeth and these grow more distinct downwards; 

 at the same time a second row of teeth gradually shows itself along the outer row. These teeth 

 form the lateral extremities of the growth ridges, which here generally run parallel to the basal 

 margin. The same ridges run parallel to the scutal margin of the valve on the other part of the 

 fixed tergum, viz. that part which lies between the ridge and the fixed scutum. 



The fixed scutum has a pointed and distinctly beaked apex and is composed of a broader, 

 nearly flat, triangular portion and a narrower inflected portion which only widens somewhat 

 towards its inferior extremity. The tergal margin is hollowed out and furnished with a row of 

 teeth, which project over the margin of the tergum and which stand at the place of the kind 

 of radius developed at the tergal margin of the scutum in other species of Vcrruca. The ridges 

 of growth are distinct, their direction is very irregular, yet they, generally, run parallel to the 

 basal margin of the valve. In the inferior part of the valve these growth ridges are produced 

 laterally into distinct teeth, forming together a row which runs nearly parallel to the row of 

 teeth which was compared with the radius of the scuta of other species of Verruca. Here and 

 there, and especially on the inferior half of the surface of the fixed tergum and scutum, are ver- 

 tical folds, of varying width and of a very unequal distinctness. 



The basis of the shell is elongately oval in shape and is, probably, membranous, as 

 in the other species of the genus. The large specimen is attached to a bundie of presumably 

 siliceous needies, the smaller to a single slightly stronger needie. 



The si ze of the large animal can be judged from the following dimensions : height 

 1 1 mm., distance from the apex of the rostrum to that of the carina 9.5 mm. The young 

 specimen has the same dimensions 2.9 and 3 mm. respectively. 



A figure of the young specimen is given on PI. XII, fig. 6. I think there can be no doubt but 

 that it really is a young specimen of the species described above. The general shape of the shell 

 and of the different valves is already much like that of the full-grown animal. The differences are 

 to be considered as caused by the difference of age. Briefly, these differences are as follows : 



1 the intermediate articular ridges of the tergum, i. e. those between the axial and the feebly 

 indicated ridge along the shorter occludent margin are partly developed only : in fact their 

 basal portions only can be made out; 



2 the articular ridges of the scutum also are only partly developed ; 



3 the rim running over the rostrum from the carino-basal angle to the apex is still wanting, 

 the lines of growth in the upper and lower triangular portions of the valve being still 

 continuous; and 



4 the furrow of the carina is represented by a rather indistinct line only. 



For the study of the growth of the valves of species of this interesting genus, and for 

 the determination of younger specimens also of other species, I thought it would be of interest 

 to point out these differences for the present species. 



