28 M. J. de Guerne on the 



IV. — Monographic Note on the Rotifera of the Family 

 Asplanclinida3. By M. Jules de Guerne *. 



As previously indicated, one of the most remarkable types 

 of the pelagic fauna of the Lagoa Grande is a new Rotifer of 

 the genus Asplanchna. I give the description of it below, 

 and follow it with a summary investigation of the family 

 Asplanchnidge. Having been struck long since with the fact 

 that its representatives exist in almost all lacustrine faunas, I 

 had collected numerous documents upon most species of the 

 group. The present work furnishes a very natural oppor- 

 tunity to coordinate these. 



Asjjlanchna Imhojiy sp. nov. (Fig. 1.) 



Diagnosis. — Femina. Corpus ovato-globosum, pellucidum ; maxiUse 

 duobus tantum ramis compositie, robustae, elongatse, apice paulu- 

 lum incurvato, bifido ; rami in medio unco valido interno armati ; 

 ramorum basis triangularis, solida, hamulo extorno superne in- 

 structa. 



Mas ignotus. 



Long. mill. 0-45-0-50, lat. mill. 0-30-0-35. 



The dimensions, taken from specimens fixed by osmic acid 

 or plunged while alive into alcohol, are certainly below the 

 reality. The animals have undergone a violent contraction 

 and must be much larger when alive. 



The body is globular and extremely transparent, with the 

 exception of the stomach, as in all the species of the genus. 

 I have seen no oculiform point. The masticatory apparatus, 

 composed only of two pieces, is very characteristic ; it differs 

 from that of all known Asplanchnce (fig. 1) ; its form is con- 

 stant, and I have observed it in a great number of specimens. 



Locality. — This species is exceedingly abundant in the 

 produce of pelagic fishings made in the Lagoa Grande at 



* Extracted from a volume published at the cost of His Highness 

 Prince Albert of Monaco, who has been kind enough to permit us to 

 translate this chapter. The work is entitled ' Excursions Zoologiques 

 dans les iles de Fayal et de San Miguel (Afores),' and the materials for 

 it were collected by the author during the third scientific expedition 

 into the North Atlantic, made in 1887 by His Highness Prince Albert 

 of ]Monaco in his yacht ' I'nirondolle,' the Prince having invited M. 

 Jules do Guerne to accompany him as zoologist. 



