230 ON A LARGE PENELLA-SPF.CTES. 



at all how much the parasites of this genus are liable to 

 an important variation in form, when the chance guides 

 them upon one fish or the other and when they fix them- 

 selves into the soft flesh or under such unfavourable 

 conditions, as apparently presented by the fins." In the 

 catalogue of Parasitic Copepoda found on fishes, published 

 in 1899 by Mr. Bassett-Smith ') only six species are re- 

 corded, but the number of specific names mentioned in 

 the Zoological litterature, undoubtedly is twice as great, 

 their diagnoses however being often so indefinite, that it 

 is impossible to recognize the species referred to. I there- 

 fore think it the best to describe our specimens as accu- 

 rately as possible and to compare them with the well- 

 known species. If a later examination may prove that they 

 represent a new species, I propose to call it P. Nouhuysii 

 in honour of the amateur-naturalist , who enriched our 

 collections with several interesting specimens. 



The largest female specimen (no males are observed) 

 has a length of about 170 mm., its cephalothorax mea- 

 suring nearly 80 mm., its genital segment 60 mm., and 

 the abdomen 30 mm. It is the greatest length of a 

 P^rjé/Za-species hitherto recorded from a fish, for P. histio- 

 phori Thomson ^), found upon Histiophorus Herscheli, mea- 

 sures only 90 mm.; those living on warmblooded animals 

 appear to be larger, for the not quite full-grown speci- 

 mens of P. crassicornis St. L. (a parasite of Hyperoodon 

 rostratus) have a length of 80 to 100 mm. and the spe- 

 cimens of Pejulla halaenopterae, described by Koren and 

 Danielssen had the enormous length of 300 to 320 mm. 

 According to Messrs. Anthony and Calvet, a Balaenoptera 

 physohis, caught at Cette in October 1904, bore on the 

 flanks of its body several Penell a-specimens, 100 to 150 



often called «Dolphin" by the seamen; misled by that name Messrs. Anthony 

 and Calvet (Bullet. Mus. d'Hist. Nat 1905) thought that it was met with 

 upon a cetaceous mammal, belonging to the genus Delphiuus. 



1) Pjoc. Zool. Soc. 1899, p. 482 



2) Trans. N. Z. Inst. Vol XXII, 1889, p. 368, pi. XXVIII, fig. 2. 



Notes from the Leyden M^useum, "Vol. XXVI. 



