Akademie der Wissenschaften zu Berlin. 405 



of the Mammalia ; that of the Proteae and the Caecilia, on the Amphibia ; that 

 of the Cyclostomata, on the fishes ; and that of the Lerneae on the Crustacea. 

 The Cyclostomata are, however, doubly interesting, as they at once occupy the 

 extreme limits of the fishes, and form the Jink between the vertebrate and in- 

 vertebrate animals. So great uncertainty has hitherto prevailed with regard to 

 them, that they have been placed in four different classes by naturalists, viz. 

 amongst the Pisces, the Amphibia, the Mollusca, and the Vermes. The Myxine 

 glutinosa was first noticed upon the coasts of Greenland and Norway by Kalm, 

 and was described by him as a species of Lamprey. Linne gave it the name 

 which it still bears, but classed it amongst the Vermes. Modeer placed it 

 amongst the Amphibia. Retzius thought it ought to be placed in the same class 

 as Petromyzon, agreeing with Linne in opposition to Camper, that it comes 

 nearer to Vermes than to Pisces, and that it might without difficulty be sepa- 

 rated from the latter. F. O. Midler classed it with the Mollusca, probably on 

 account of the presence of tentacula. In the edition of the Fauna Suecica by 

 Retzius, the Myxine is placed amongst the Pisces. The object of the present ela- 

 borate treatise is to obviate these uncertainties, and from a careful anatomical 

 examination, to assign to it its true station in the animal kingdom, as well as to 

 corect some errors and oversights which appear in the remarks of Bloch, Du- 

 meril, Sir E. Home, and other writers upon the subject. Before proceeding to 

 anatomical details, the author gives a classification of the cartilaginous fishes, 

 and particularly of the Cyclostomata, in which the Myxine is placed in confor- 

 mity to its internal structure. He divides the cartilaginous fishes into four orders, 

 and with regard to the sharks follows Cuvier's arrangement of the genera, 

 though he thinks that, judging from the varieties found in the Mediterranean 

 alone, that great naturalist has not made them sufficiently numerous. 



CHONDROPTERYGIA. Skeleton cartilaginous; cranium without sutures. 



I. Order. Branchiostega. 



1. Family, Cataphracta — Cartilage of the cranium, and skin of the 

 trunk covered at intervals with cartilaginous tubercles. 



Sturiones. Genus 1. Sturio — with Brandt's subgenera, Huso, Sturio, 

 Sterleta, Helops. 



2. Fam. Nuda — Body without tubercles. 



Spatulariae. Genus. 2. Spatularia with the subgenera, Polyodon, Lacep. 

 and Planirostra, Rafinesque, Icth. Ohiensis. 



II. Order. Holocephala. 



Genus 1. Chimaera. 



2. Callorynchus. 



III. Order. Plagiostomata. 



1 . Family. Squall The branchial apertures not fixed to the head. 

 Genus 1. Squalus, with Cuvier's subgen. Scyllium, Carcharias, Lamna 

 Galeus, Mustelus, Notidanus, Selache, Cestracion, Spinax, Centrina, 

 Scymnus. * 



2. Zygaena, Cuv. 



3. Squatina. Dum. 



4. Pristis. Lath. 



* The toothless Sharks, Aodon, Lacep,, Massassa and Kumal, Forsk. are 

 still doubtful. 



NO. IV. D d 



