225 ON SOME NEW AND RARE COPEPODA FROM THE CLYDE 
creatures to be found within their limits is approximately 
complete. No doubt the vertebrates and the larger of the 
invertebrates have been more or less exhaustively studied, 
so that additions to the number of species already known are 
now rarely met with; but in regard to the more minute 
invertebrates the case is different, and it is to these that 
our remarks chiefly apply. Of the various groups of these 
minute organisms, that of the Copepoda is perhaps one of the 
most interesting and most likely to reward the systematist 
with the discovery of new forms. 
In the present contribution we give, as far as appears 
necessary, a brief account of the details of structure of two — 
apparently undescribed Copepods from the Clyde, and new 
records for some rare species already described. The first. 
we propose to describe is a species of Delavalia, viz :— 
DELAVALIA GIESBRECHTI, sg. mov., Plate 1V. Figs. 1-10. 
Description of the Female.—Length -45 mm. (s'5 of an inch). 
Antennules moderately stout, eight-jointed. The proportional 
lengths of the joints are approximately as follows :— 
Proportional lengths of the joints 9 10 8 6 5 © 5 7 
Numbers of the joints I 2 3 4 <5) sone 
Antennz somewhat like those of Delavalia emula, T. Scott, 
but the secondary joints, which are three-jointed, are rather 
more slender than in that species. The mandibles—the 
structure of which is characteristic of the genus—have the 
principal seta at the end of the apical branches of the palp 
spiniform and of considerable length, while the lateral branches 
appear to be two-jointed, the end joint being very small 
(Fig. 4). Posterior foot-jaws very small, and armed with a 
small terminal claw (Fig. 6). First pair of swimming feet 
somewhat similar to those of Delavalia palustrts, Brady, but 
the first joint of the inner branches is proportionally shorter 
and the second joint longer and narrower than in that species ; 
the second joint is also furnished with a moderately long 
spine and a plumose seta at the apex and two plumose setae 
on the inner margin, while a similar seta springs from the 
inner distal angle of the first joint ; the outer branches are 
armed somewhat similar to those of Delavalia palustris (Fig. 7), 
