266 JAniuean Society, 



Mr. Owen observed, that since the time of the discovery of the 

 Omithorhynchus there had not been submitted to naturalists a spe- 

 cie •> which proved more strongly the necessity of a knowledge of its 



whole organization, both external and internal, in order to arrive at 

 a correct view ofits real nature and affinities, than did the Lcpidosiren, 

 and as he had felt a reluctance to bring before the Society an in- 

 complete description, which might only have served to raise new 

 doubts in the minds of naturalists with regard to this animal, he had 

 deferred since June 1837 the completion and communication of the 

 present paper. He had however at that time prepared a brief descrip- 

 tion of the specific characters of the specimen in question, under 

 the name of Protoptcrus, and had referred it in the Catalogue of the 

 Museum of the College of Surgeons to the Class of Fishes, on ac- 

 count of its scaly covering and the condition of its nostrils as plicated 

 sacs, and to the abdominal family of the Malacopterygian order 

 of that class, in which it seemed to present an extreme modification 

 or rudimental condition of the fins indicative of a transition from the 

 abdominal to the apodal families. 



The anatomical details which formed the principal part of the present 

 communication, confirmed the propriety of referring the Lepidosiren 

 to the class of fishes ; but they also led, Mr. Owen observed, to a con- 

 siderable extension in his original views of its affinities in that class. 



A minute description was then given of the external characters 

 and peculiarities of the present species, which differed from the Le- 

 pidosiren paradoxa in the greater relative length of the head and ru- 

 dimental fins as compared with that of the trunk ; and in its general 

 size, which is three-fourths smaller. 



The chief peculiarities of the skeleton consist in its imperfect, or 

 rather partial ossification, and in the green colour of the ossified 

 parts ; in which it resembles that of the gar-pike (Belone vulgaris). 

 The parts which continue permanently in the cartilaginous condition 

 are the petrous elements of the temporal bones containing the acoustic 

 labyrinth, a portion of the articular pedicle of the lower jaw, the 

 branchial arches, and the bodies of the vertebras : these, moreover, are 

 not separated to correspond with the neurapophyses and ribs, as in 

 Plagiostomous Cartilaginous Fishes, but retain their primitive con- 

 fluent condition as a round continuous chord, extending from the oc- 

 ciput to the end of the tail : this vertebral chord consists of an ex- 

 ternal firm, elastic, yellowish capsule, enveloping a softer subgelati- 

 nous material, as in the Cyclostomous Fishes. The corresponding 

 parts or basilar elements of the cranial vertebras were ossified : and 

 Mr. Owen then entered upon a detailed description of the skull. 



