CRUSTACEANS 



with Mr. Tomalin, for he says: ' In fact, I have observed that the well- 

 fed Argulus can spend many days or even weeks separated from its host 

 without nourishment.' ' 



Our next species belongs to a far more important division of the 

 Branchiopoda, namely, those which from their divided or biramous second 

 antenna are called the C/addcera, or ' branching-horns.' These include 

 many families, numerous genera, abundance of species, and of individuals 

 innumerable millions. Though this part of the population of North- 

 amptonshire would defy the efforts of any census, it has attracted so 

 little attention that I can only find a single record of a single species. 

 This belongs to the family Sidida, which comprises seven genera. The 

 genus Sida, Straus, from which the family name is derived, has indeed 

 only one species, Sida crystallina (O. F. Miiller). But, to make up for this 

 paucity, you may go from Northamptonshire to Nantes and to Norway, 

 you may visit Berne and Berlin, you may travel to Moscow, to Shanghai, 

 to Lake Superior, and at all these places, in small reservoirs, on the 

 margins of ponds or in large lakes, meet with this little oblong trans- 

 parent species, passing- through the water with ' a sort of rapid running 

 movement,' or afSxed to water-weeds by an adhesive apparatus at the back 

 of its head. Dr. Baird mentions among the places at which it has been 

 taken in our islands, ' Back fish-pond at Overstone Park, Northampton- 

 shire, July and August, 1849.'^ 



Among the Copepoda, as among the Cladocera, there are several 

 species of so general a distribution that their occurrence may be predicted 

 as much in one county as in another, and the notification of it in any 

 particular locality is almost a matter of chance. It is therefore an odd 

 coincidence that Dr. G. S. Brady in his British Copepoda should not 

 expressly record for this county any of the common and well-known 

 species, but on the other hand should record for it one that was, at any 

 rate at the date of his book, a new and rare one. In 1880 he winds up 

 the description of his Canthocamptus trispinosus, n. sp., with the words, 

 ' Length one twenty-fifth of an inch (one mm.). Male unknown,' and 

 observes, ' the only known locality for this species is the river Nene at 

 Peterborough, where I took it sparingly in a little woody inlet." It 

 belongs to the family Harpacticidce and to the genus Canthocampus 

 instituted by J. O. Westwood in 1836. The name is evidently com- 

 pounded of two Greek words meaning a thorn and a bend, since West- 

 wood himself explains that the species ' have the abdomen of the females 

 recurved with a spine beneath at the base.' * On pretence of correction 

 authors have since almost invariably falsified the spelling into Cantho- 

 camptus, changing the second half which is not really wrong and leaving 

 unaltered the first half, which is evidently derived from acantha, a spine, 



' Zeitichiift far tvissenschaftliche Zoolope, vol. xxv. p. 277 (1875). 



^ Baird, British Entomostraca, Ray Soc, p. 109, 1850; Dr. Jules Richard, Annaks da Sciences 

 Nalurelles, Zoologie, ser. 7, vol. xviii. p. 336 (1895). 



3 Brady, A Monograph of British Copepoda, Ray Soc, vol. ii. p. 55, pi. 45, figs, i 5-22- 



* J. O. Westwood, The Entomologist's Text Book p. l 1 5 (1838); Partington's Cycloptedia, Art. 

 'Cyclops' (1836). 



105 



