36 DE. T, S, COBBOliB ON XllEMATOBE PAliASilKS 



cimens, whose examination will in all likelihood yield interesting 

 results. 



The first trematode that I proceed to notice is the species 

 termed Distoma lancea by the late C. M. Diesing. His descrip- 

 tion was based upon the examination of several parasites found 

 by the Brazilian traveller Natterer. They were discovered in the 

 biliary ducts of a male Dolphin dissected at Barra do Eio JSTegro 

 on the 29fch of December, 1833. Natterer calls this cetacean the 

 Tacuschi, and in a letter to Diesing names the species Delphinus 

 tacuscM in order to distinguish it from the D. amazonicus of Spix 

 and Martins. 



In all cases of parasitism it is desirable, when possible, to get 

 accurate information as to the species of host infested. Accord- 

 ingly I have sought Professor Elower's assistance ; and he informs 

 me that there are certainly two, if not three, species of Dolphin 

 inhabiting the Amazons. In his paper in the ' Trans. Zool. Soc' 

 vol. vi. p. 87, he has shown that Spix and Martius's JD. amazonicus 

 is clearly referable to the Inia or Bolivian Dolphin {Inia Geof- 

 froyi). Thus far the views of Flower, Natterer, and Diesing are 

 in agreement ; moreover the geographical position of Barra 

 shows that the Dolphin in question could not be the Inia, since, 

 as Blyth long ago remarked, this form " inhabits only the remote 

 tributaries of the Amazon and the elevated lakes of Peru." Seve- 

 ral other species from this river have been described, one of 

 these being placed by Mr. G-ray in a separate genus, and named 

 by him Steno tucuxi. Prom the specific title there can, I think, 

 be little doubt that Gray's cetacean answers to the Delphinus 

 tacuschi of Natterer; but Professor Plower is of opinion that 

 Gray's species is an ordinary DelpJiinus, in the sense in which that 

 genus is now commonly restricted. In this case it may, he thinks, 

 probably be referred either to the D.fluviatilis or to D. pallidus. 

 Whichever view is correct, it is clear that batterer's parasite was 

 obtained from a thoroughly fluviatile cetacean, and not from an 

 oceanic or even an estuary form. 



From Diesing's original description, I am led to infer that 

 Natterer had carefully examined several Dolphins, with negative 

 results as regards the presence of flukes ; at all events it is ex- 

 pressly stated that he found the Distoma lancea " once only," 

 when numerous examples of the parasite were secured. Dr. 

 Anderson's specimen was a solitary one, procured from the short- 

 snouted Dolphin {Orcella hrevirostris, Owen). He obtained it 



