Thomson. — Oyi Parasitic Copepoda. 353 



Plate XXIV. 



Figs. 1 and 2. Top and side view of the pelvis of the supposed hybrid fowl. 



Half natural size. 

 Figs. 3 and 4. Corresponding views of the pelvis of Ociidroums aiistralis. 



Only reduced two-thirds natural size. 

 Fig. 5. The sternum of the supposed hybrid seen from below. Of half 



natural size. 

 Fig. 6. Similar view of the sternum of 0. aiistralis, but of natural size. 

 Fig. 7. Side view of sternum of the said hybrid. Half natural size. 

 Fig. 8. The same of 0. aiistralis, but of natural size. 

 Fig. 9. Eight scapula (sc), coracoid (c), and furcula (/), with (It) hypo- 



cleidium, of the supposed hybrid fowl. External view, reduced 



half natural size. 

 Fig. 10. The same bones of Ocydromus. Of natural size. 



Akt. XLIII. — Parasitic Copepoda of New Zealand, with 

 Descriptions of Ne^v Species. 



By Geo. M. Thomson, F.L.S. 



[Read before the Otago InstittUe, 12th November, 1889.] 



Plates XXV.-XXIX. 



Our knowledge of those forms of Crustacea which constitute 

 the order Copepoda is limited — as far as this colony is con- 

 cerned — to what is contained in papers of mine published in 

 former volumes of the New Zealand Institute " Transac- 

 tions " — viz., "On the New Zealand Entomostraca," vol. xi., 

 pp. 251-263; and " New Zealand Copepoda,'' vol. xv., pp. 

 93-116. The forms referred to there belong to the free-swim- 

 ming section of the order, or, if parasitic, they are only ecto- 

 parasites, attaching themselves for a limited period of time to 

 the outside of the body of their host, and not losing the power 

 of free movement. Those to which I wish to draw attention 

 in this paper are sedentary creatures (except in very young 

 stages), living in the mouth-cavity, or among the gills or the 

 muscular tissue, or even in the alimentary canal of their 

 hosts, and exhibiting varying degrees of retrogression in their 

 development. Indeed, in the very greatly degraded forms be- 

 longing to the families Coyidracanthina and LernceopodidcB, the 

 external form and structure have become so altered and de- 

 generated that it is only by a study of the individual develop- 

 ment that their affinities can be determined. In the present 

 paper no attempt in this direction is made. The object is 

 merely to record the occurrence of various species of these 

 parasites, and thus to widen the ever-extending field of our 

 knowledge of the fauna of these islands. 

 23 



