222 PROF. J. K. GUEENE ON THE MUTUAL EELATIONS 



mucous ducts ou the head are among tlie most prominent of its 

 piscine tendencies. 



Several characters, also, are presented by Lepidosiren, which, 

 although more or less ichthyic, are not inconsistent with the notion 

 of its being an Amphibian. These, with scarcely an exception, are 

 as follows : — 



1. The presence of an intestinal spiral valve. As Professor 

 Owen* has remarked, "there is good evidence that the 

 intestine of the Ichthyosaurus was provided with a spiral 

 valve, yet it is not on that account regarded as a Fish." 



2. The persistent notochord. 



3. The absence of occipital condyles. This and the preceding 

 condition occur also in Archegosaurus. 



4. The arrangement of the muscular system. On this head 

 Professor Owen justly observes, " that although the muscles 

 of the trunk are quite fish-like in their disposition, yet 

 the lower Perennibranchians and the larvae of the higher 

 Batrachia ofler a similar agreement in this part of their 

 organization to the class of Fishes." He adds also that 

 the muscles of the mandibular, hyoidean, branchial, and 

 scapular arches " resemble in some points the arrangement 

 of the same muscles in the Perennibranchians, and in other 

 points that in the true Fishes." 



5. The simple structure of the auditory apparatus. A like 

 organization of the same parts may be seen among the 

 Perennibranchians . 



6. The conditions of the generative organs. Professor Owen 

 has shown that " the structure of these organs in the Lepido- 

 siren, while it shows its near affinity to the Reptiles, by no 

 means proves that it is not a Fish." 



7. The structure of the teeth. These are said to " differ from 

 any known dental apparatus in the class of Fishes in the 

 modifications of the working surface, which at once adapt 

 them for piercing, cutting, and crushing." 



8. The bipartite cellular air-bladder or lung. ISTo comment 

 seems needed on the significance of this apparatus, which, in 

 spite of its highly developed condition, bears so close a 

 resemblance to the air-bladder of the Ganoids ; in fimction, 

 however, the au'-bladder of Lepidosiren is more truly a lung 

 than that of Amia or any other Fish. 



* Description of the Lepidosiren anitectens, Linuean Transactions, 1841. 



