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THE ROYAL SOCIETY OF CANADA 



inner and outer rami consisting of three joints. The basal joint 

 has a single spine at its outer distal angle, but none on the 

 inner side. On the outer ramus there is a single curved spine 

 near the outer distal angle on the first and third joints, but 

 none upon the middle joint, whose outer border is smooth, except 

 for a few hairs. The terminal joint is somewhat expanded and 

 bears five terminal setae, all of which have basal 

 enlargements and a single seta takes its origin from 

 the inner border of both the second and first joint. 

 On the inner ramus there are three terminal setae, 

 and one on either border of the terminal joint, and 

 single setae also arise from the inner borders of the 

 first and second joints, the outer borders of these 

 joints being unarmed. 



No trace could be found of a fifth thoracic 

 appendage. 



Of the Monstrillas described from northern 

 waters^ the males of three are as yet unknown, while 

 from those of the others (M. longicornis I. C. 

 Thompson, M. grandis Giesbr. and M. anglica Lub- 

 bock) that of M. canadensis differs greatly in the form 

 of the antennae and of the genital segment and in the 

 absence of the fifth pair of thoracic appendages. 

 Whether M. canadensis will prove to be identical with 

 M. gracilicauda Giesbr., M. intermedia Aur., or M. 

 helgolandica Claus must remain unsettled until either 

 the males of these species or the female of canadensis 

 are definitely determ.ined; the indications are, how- 

 ever, in favor of its distinctness. 



Fig. 6. Monstrilla 

 canadensi s . 

 Thoracic 

 appendage. 



2. Hansen's y iv larva. 

 The first record observed of the larvae described by Hansen as 

 Type y larvae, was made by Hensen^ who referred certain examples 

 taken in the North Sea to the copepodan family Corycaeidae. The 

 first detailed description was, however, that given by Hansen^ who 

 contributed accounts of several forms, apparently belonging to 

 different species, from West Indian and South Atlantic waters, 

 and also of a form taken in the Bay of Kiel. He discussed at length 



ip. J. van Breemen, Copepoda, Nordisches Plankton, VIII, 19. 



^V. Hensen, Ueber die Bestimmung des Planktons. — Ber. Comm. wissensch, 

 Untersuch. der deutschen Meer. V. 1887. 



'H. J. Hansen, Die Cladoceren und Cirripedien, Ergeb, Plankton Exped. H 

 g. d. 1899. 



