RECENT BRITISH OSTRACODA. 



467 



above, subovate, widest in the middle ; greatest width equal to a little more than half the 

 length. End view ovate, width equal to three-fourths of the height. Notch, as seen 

 from below, elliptical, seen from the front arcuate. Shell covered densely with short 

 pubescent hairs ; colour yellowish white. Second joint of the upper antennse about as 

 long as the following four united ; secondary branch of the inferior antennae very small, 

 the last joint elongate- ovate, bearing two setae on its anterior margin, and one, which is 

 curved upwards, on the truncate extremity. Last joint of the mandibular foot armed 

 with three claws, the anterior of which is short, the other two subequal, and nearly twice 

 as long ; second joint bearing at its apex a large subconical process, which is armed at 

 the extremity with two moderately long plumose setse ; oviferous feet bearing about 

 twenty-four apical setae, each of which has 4-6 series of short teeth ; extremity hooked 

 at one side. Postabdominal plates having 8-10 dentate claws. " Male similar to the 

 female, but rather smaller, tlie eyes larger and redder ; secondary branch of the lower 

 antennae three-jointed, last joint elongated, membranaceous, terminating in two short 

 setae." 



Length i^i- ' Jt'vwv- 

 Hab. Forty or fifty miles off Tynemoutli, on a muddy bottom {Rev. A. M. Norman) ; " dredged in from 

 80 to 90 fathoms sand, 20 miles east of the Noss, in the Shetland Isles" {R. M' Andrew, Esq.). 



I have not had the opportunity of examining the type specimens of this species ; but 

 as I believe Dr. Baird considers them to be identical with £. glohosus, I have here 

 adopted that view. 



The following interesting remarks on this species I translate from Sars's Avork on the 

 Norwegian Ostracoda. The difference noticed by that author between the two forms 

 (probably male and female) have an important bearing on those which I have myself 

 found in Cylindroleheris Ilarice. In the latter species, however, the variation occurs 

 principally in the upper antennae. " On account of its slow movements and inconspi- 

 cuous colour, this species \^B. globosus] is somewhat difficult to detect amongst the mud 

 in which it constantly seems to live, and with which its shell is often more or less coated. 

 I have mostly found the setae of the lower antennae, as represented in Lilljeborg's figure, 

 very short, decreasing in length towards the apex, and non-plumose ; but in one indi- 

 vidual, which in other respects agreed with the rest, I found a remarkable variation, the 

 setae attached to the last five joints being much elongated, and adapted for swimming. 

 My attention was first drawn to this as follows. Among several specimens which I had 

 in a glass of sea-water, I saw, to my surprise, one individual suddenly abandon its slow 

 creeping movement, which, from the structure of the lower antennae, I had alone thought 

 possible for this genus, and, with a peculiar rolling movement, give a short bound 

 upwards from the bottom of the glass. On examination of the animal, I found that the 

 lower antennae were armed with long swimming-setae. On account of this peculiarity, 

 I thought that the specimen might possibly be a male, but did not find this surmise 

 borne out by anatomical examination. I have since found amongst my preserved spe- 

 cimens many individuals thus fitted for swimming, and have convinced myself that those 

 with the short setae are females. The peculiarity is not one of age merely, for I have 

 found it in both young and old individuals ; and I have noticed it also in another species 



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