ON THE GENUS LERNzEODISCUS. 429 



The Genns Lermeodiscus (F. Miiller, 1862). 

 By Geoffrey W. Smith, M.A., F.L.S. 



(Plate 38.) 



[Read 7tli May, 1914.] 



The genus Lernceodiscus was created by F. Mllller in 1862 (1) for a Rhizo- 

 cephalons parasite found by him on a Porcellana from Brazil. He did not 

 describe the internal anatomy of the parasite, and nothing more was known 

 about it until I gave an account of the genus in my Monograph of the 

 Rhizocephala in 1906 (2), based on some specimens found on Galatliea 

 dispersa at Naples, on G. intermedia from Norway, and on G. strigosa 

 from Naples. Since the appearance of this work two French authors have 

 added to our knowledge of the genus, Dr. Max Kollmann (3 & 4) and 

 Dr. Guerin-Ganivet (5). These authors have accepted the account I gave 

 of the anatomy, but Dr. Kollmann disagrees with my interpretation of the 

 orientation of the parasite and offers a different one. 



The re-examination of the question which is here undertaken is due to 

 Professor W. A. Herdman, who found a specimen of Rhizocephala upon a 

 Munida hamfica from the Shetlands and sent it to me for identification. I 

 had previously seen two Rhizocephalous parasites on Munida, and described 

 them as a new genus Triaiigulns in my monograph (2, p. 115) ; but since 

 I was only able to study these two specimens (which were not very well 

 preserved) macroscopically, I was in considerable doubt as to the correctness 

 of my diagnosis. I was anxious therefore to study Professor Herdman's 

 specimen by means of serial sections, which he very kindly permitted me to 

 do, and the result of this examination has been to show that this parasite of 

 Munida really agrees in all essentials with the Lermeodiscus on Galatliea and 

 should be included in that genus. The genus Triangulus must therefore be 

 withdrawn, and the parasites hitherto described as Triangulus munidce should 

 be named Lernwodiscus munidce. 



At the same time a careful examination of Professor Herdman's specimen 

 and a re- examination of my preparations of Lerna'odiscus galathea;, have 

 shown that I have made an error in my description and figure published in 

 my monograph with regard to the position of one of ihe genital openings. 

 This error certainly led me astray in the interpretation I put upon the 

 orientation of the parasite, and I have now no doubt that Dr Kollmann's 

 correction of my interpretation is amply justified, and that his own view is 

 essentially right. 



It is hoped, therefore, that in this paper the anatomy and systematics of 

 the Rhizocephala hitherto found on the symmetrical Anoninra may be 



