LIST OF THE NON-PARASITIC MARINE COPEPODA. 423 



the left thoracic expansion is preserved, and which is represented 

 as if seen through. 



Fig. 2. Outline of a scale of Platysomus ?-otundus, considerably enlarged. 



Fig. 3. Outline of a scale of Platysomus Forsteri, enlarged. 



Fig. 4. Outline of a mandibular ramus of Ccelacanthus lepturus, slightly 

 enlarged : o, articular piece ; b, glenoid surface ; c, dentary bone ; 

 d. teeth. The articular piece and dentary bone are laid together 

 in their natural positions, but not united ; so that the form and 

 extent of each can be distinctly traced. 



PLATE XVI. 



Fig. 1. Scale, natural size, of Ctenodus (first species) : a, anterior margin ; 

 b, posterior or exposed ditto ; c, marginal border ; d, rapture 

 exposing cast of upper surface ; e, central area. 



Fig. 2. Scale, natural size, of Ctenodus (second species) : a, anterior mar- 

 gin ; b, posterior extremity ; c, marginal border ; d, central 

 area : the dotted line indicates the form and extent of the scale. 



XIX. — A List of the nonparasitic marine Copepoda of the North- 

 east coast of England. By Geo. Stewardson Brady, C.M.Z.S. 

 (Plates XVH.-XXI.) 



The following list, though embracing all the species at present 

 known to me as inhabiting our district, must be taken only as 

 an instalment of what an exhaustive survey would no doubt re- 

 veal. The examination of these little creatures is exceedingly 

 tedious and laborious, the points of difference being often in- 

 distinguishable except with tolerably high microscopic powers. 

 Thus a very small gathering, if it contain any great variety of 

 species, will often occupy many hours in its examination. 



By far the greater number of species here noted, or described 

 by foreign authors, are free - swimming animals; some have a 

 special predilection for the fronds of fuci, and others for muddy 

 localities or the bed of the sea, but little is yet known of the 

 ground-inhabiting forms, and among them there remains doubt- 

 less a rich harvest for future collectors. 



