CRUSTACEANS 



pulchella. Leach, has been obtained by Dr. Sorby in the River Orwell. For a long time the genus 

 Jassa of Leach was confounded with his Podocerus, established at the same time, but really belong- 

 ing to a different family.''* Lastly, for the family Corophiidae a record is supplied by the Rev. E. N, 

 Bloomfield, who, writing in August 1 902, says, 'in a very interesting letter from Dr. Harmer, 

 F.R.S., of Cambridge, among various creatures met with by him in the salt water ditches near 

 Aldborough, he mentions the very remarkable amphipod Corophium grossipes.'' This species should 

 rather be called C. volutator (Pallas). All round our coasts it forms its tubular galleries in the 

 mud of tidal swamps. From C. crassicorne (Bruzelius), which has been taken in almost fresh 

 water in Norfolk, C. volutator is separated by a rather uncommon feature of distinction, the latter 

 species having the fourth, fifth, and sixth segments of the pleon normally articulated, while in the 

 former they are coalesced into a single piece. 



The Entomostraca form three principal groups, Branchiopoda, Ostracoda, Copepoda, each with 

 various subdivisions. In the first only the Cladocera now need our attention. Of these the 

 following examples may be specified. From a small pond near Oulton on 1 4 May 1 907, a specimen 

 of Daphnia pulex (De Geer) was taken, corresponding with the figure given by Lilljeborg of a 

 young male taken at Upsala, not in the spring but early in September, and described as Mas junior 

 autumnalis?^ To the same family Daphniidae belongs Simosa vetula (O. F. MuUer), of which 

 specimens were obtained from a ditch near Oulton, 13 May 1907. These agree perfectly with 

 Lilljeborg's account and figures of the femina adulta vernalis.^ The veteran Swedish anthor states 

 that the female of this species, like Daphnia pulex, is largest in the spring, being about 3 mm. 

 long, and having then the largest number of eggs in the brood cavity, its shape broad oval, strongly 

 narrowed in front. In this genus it may be noted that the four-jointed branch of the second or 

 swimming antennae has one of the apical setae shorter than the other two, minutely uncinate 

 and thereby prehensile. On the hind body S. vetula has two processes, the anterior standing nearly 

 upright, the other smaller, bent forward. Behind the caudal setae the upper margin of the tail-piece 

 runs to an angle, between which and the ungues a very sinuous border carries from nine to ten 

 spines. The ungues are distinguished from those of other species in the genus by the microscopic 

 fineness of their spinules. The name vetula, as given by Mailer, may originally have included 

 more than one species. As defined by Schoedler in 1858 it is now generally accepted for the form 

 here described. A male specimen was obtained, as well as several of the other sex. In the family 

 Chydoridae, at the same time and place with S. vetula one example of Eurycercus lamellatus (O.F.M.) 

 was taken. This family differs from the Daphniidae by having both branches of the swimming 

 antennae instead of only one of them three-jointed, and by having the intestine with instead of 

 without a loop. Eurycercus agrees with the Daphniidae in that the intestine has in front two 

 caecal appendages, which are not present in other members of the Chydoridae. E. lamellatus has the 

 first antennae thick, with the sensory seta placed near the middle of their single joint. Lilljeborg gives 

 the length of the female as ranging between 3 and 4 mm., the size somewhat larger in spring and 

 summer than in autumn, less in brackish water than in fresh." Under the microscope the tail-piece is 

 a pleasing object with its fringe of 1 00-120 spinules. These gradually increase in size as they pass 

 from the caudal setae to an angle which is separated from the ungues by a deep sinus. Near the 

 ungues the sinus also carries spines and spinules. Chydorus sphaericus (O.F.M.), a tiny dwarf in 

 comparison with the two preceding species, is abundant at Lowestoft, as it appears to be in suitable 

 waters all over the globe. The sexual differences in this species are well marked, the rostrum of 

 the female being acute, that of the male obtuse, and the tail of the male being strongly emarginate 

 at the anal fissure, instead of shallowly as in the female. 



For the Ostracoda of Suffolk, the paper by G. S. Brady and David Robertson, published in the 

 Annals and Magazine of Natural History for July 1870," is the leading authority. The authors 

 say : 'The Entomostraca of the tidal rivers of Norfolk, Suffolk, and the Cambridge fen-district con- 

 stitute so remarkable a group that it seems best to speak of them separately, and in so doing we 

 shall call the area to which we refer the East Anglian District, understanding by that term the whole 

 tract drained by the rivers Nene, Cam, Bure, Yare, and Waveney. The drainage tract of the 

 adjoining rivers on the south. Aid, Deben, Stour, &c., is separated by rising ground, and appears to 

 be zoologically distinct.' Speaking of the Broads of Norfolk and Suffolk in general, they say that 

 they may be considered as expansions of the various tidal rivers, though situated at such distances 

 from the sea as to be but slightly influenced by tidal ebb and flow. As to those with which we are 

 here more especially concerned, they write : ' Lake Lothing is a tidal expanse separated from Oulton 

 Broad, at i^s western extremity, by an embankment, through which canal boats pass by means of a 

 lock. In this way some slight communication exists between the waters of the two basins, but the 

 true outlet of Oulton Broad is by the River Waveney, which from this point takes a circuitous 



" Das Tierreich, Amph. Gamm. (1906), 21, pp. 654, 739. " Cladocera Sueciae, pi. xii, fig. 12. 



" Ibid. 167, pi. xxiv, figs. 8-18. " Ibid. 386. " Op. cit. 1-33, pis. iv-x. 



159 



