11 



him: it bears along- the inner edge a simple row of 5 natatory 

 setae, somewhat increasing- in size distally, and has too at the 

 extremity outside a strong spine. The outer joint of this branch 

 is likewise provided at the tip with a spine, though somewhat 

 smaller, and moreover bears 7 natatory setae, 4 of which issue 

 from the inner edge, the remaining 3 from the tip; of the latter, 

 the upmost is very much elongated. All the setae are distinctly 

 biarticulate and issue from separate notches in the edge. The 

 lower branch is scarcely more than half as long as the upper 

 and cylindric in :orm, consisting of 3 joints, the first however 

 very small and imperfectly defined from that succeeding it, which 

 is by far the largest. At the extremity the latter joint bears on 

 the lower side a rather long natatory seta of the same structure 

 as those on the upper branch, and, besides, a strong spine. The last 

 joint is rather small, but very distinctly defined from the pre- 

 ceding; it is provided with 4 natatory setae, 3 of which origi- 

 nate at the tip, the fourth at a notch in the upper edge. Of 

 the apical setae the lowermost is very elongated, nearly twice as 

 long as the others. 



The oral parts do not seem to differ materially from those 

 in other Sididae, and also the branchial legs exhibit a very si- 

 milar structure, as seen from fig. 5, representing one of the 2nd 

 pair, viewed from the anterior side. 



The tail (fig. 6), as in Latona, is comparatively small, usu- 

 ally not extended beyond the edges of the valves, and forming 

 only a very slight curve with the preceding part of the body. 

 It is obtusely conical in form, with the dorsal edge somewhat 

 flexuous and bulging out in its upper part. The apical claws 

 are strong and curved, each provided with 2 rather elongate 

 secondary spines. The anal denticles are very small, and affixed 

 along the sides of the tail so as scarcely to project beyond the 

 dorsal edge; they are on either side about 9 in number and 

 confined to the exterior part of the tail. The caudal setae are 

 lather elongate, distinctly biarticulate and densely ciliated; they 

 issue from separate mammilliform carneous processes originating 

 on the dorsal side of the tail, close to the point where it is 



