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Part III. — Eighteenth Annual Report 



apical and sub-apical setae. The posterior foot-jaws of the female (fig. 7) 

 have moderately short and slender terminal claws, but those of the male 

 (fig. 13) are armed with terminal claws of considerable length. The first 

 three pairs of swimming-feet 'have both branches three- jointed. The 

 inner branches, which are considerably shorter than the outer, are 

 provided with a number of seta3 on the inner margin and apex, but have 

 apparently no terminal spines ; the outer branches are also furnished with 

 several setae on the inner edge. Moreover, the first and second joints bear 

 a short but moderately stout spine on the exterior distal angle, while the 

 third joint carries two marginal and two apical spines, the inner one of 

 the two apical spines being longer and stouter than the other (figs. 8 

 and 9). In the fourth pair (fig. 10) the inner branches are reduced to a 

 single minute joint; the outer branches are also comparatively small, and 

 they want, to a large extent, the spiniform armature of the outer branches 

 of the preceding pairs. The fifth pair are small, and each consists of a 

 single one-jointed branch, which is furnished with two apical setae 



(%. ii). 



In the female the lateral processes of the fourth body segment extend 

 backward to about the middle of the penultimate segment of the 

 abdomen. This abdominal segment appears to be larger in the male than 

 in the female, as shown by the figure (fig. 14). The caudal segments in 

 both male and female are moderately elongated, being about one and a 

 half times the length of the anal segment. 



This species when living is one of the more brilliantly coloured of the 

 British Copepods, but spirit extracts the colour very quickly. 



Monstrilla (?) dance, Claparede. (PI. XIII., figs. 15-20.) 



1863. Monstrilla dance, Clap., Beobacht. iib. Anat. u. Enwickl.- 

 wirbellos Thiere an der Kiiste v. Norniandie angestellt., 

 p. 95. 



Eepresentatives of this curious genus of copepods have, as in previous 

 years, been occasionally observed in tow-net gatherings of entomostraca 

 from the Clyde. Two or three species of the Monstrillidae have been 

 recorded from North Britain, but the only one that has hitherto been 

 observed in the Clyde estuary is the species now referred to, and which I 

 have for the present ascribed to Claparede's Monstrilla dance. The 

 genus Monstrilla was added to the British fauna in 1857 by Sir John 

 Lubbock, when he described the Monstrilla anglica. For nearly thirty 

 years afterwards little or nothing further appears to have been known 

 concerning these organisms, so far at least as regards their distribution 

 in the British seas, and in view of this it is somewhat remarkable that 

 now not a year passes without a lesser or greater number of specimens, 

 representing sometimes two or three different species, being observed. 



In 1890 Gilbert C. Bourne published in the Quarterly Journal of 

 Microscopical Science a little paper on the genus Monstrilla, and gave a 

 short summary of the characters of the different forms. He divided them 

 into two groups, distinguished by the number of furcal hairs. In the one 

 group the number of setae on each furcal member is said not to exceed 

 three, while in the other there are said to be six setae on each of the 

 caudal furca. Monstrilla dance was placed by Mr. Bourne in the first of 

 these groups. 



The Clyde specimens which I record here, and which I am inclined to 

 ascribe to Monstrilla dance, do not fit in with either of Mr. Bourne's 

 groups as regards the number of furcal hairs. In the more perfect of the 

 specimens there are five hairs on each of the caudal rami, four of which 

 are prominent and one very small ; of the four large hairs, three spring 



