396 THE ANIMAL KINGDOM. 



There are three lateral lines ; a median which extends to the tip of the 

 tail ; a dorsal which always unites near the tip of the tail with the median 

 line, sometimes also anteriorly; and a ventro-lateral which extends only 

 between the fore- and hind-limbs. Each organ has a protective hyaline 

 tube in the larva, and there is at first one organ to each somite, but the 

 number increases subsequently by division. 



Cartilage persists largely in the chondrocranium of Anura : to a much 

 less extent in other Amphibia, especially in Gymnophiona. There is a 

 large basicranial and superior cranial fontanelle in Urodela, a sub-frontal 

 and two small sub-parietal fontanelles in Anura. The occipital region 

 contains two large exoccipitals which form each a cranial condyle * : a 

 small supra- and basi-occipital have been detected in some Anura. The 

 ear capsule of Anura contains a pro-, or a pro-sphen-, otic bone, to which is 

 added in Urodela an opisth-pter-otic. Proteus and one or two others have 

 an epiotic ossification as well. The middle trabecular region is ossified by 

 a sphen-ethmoid. The olfactory capsules do not unite with the ethmo- 

 nasal cartilages in Siren, Proteus, Menopoma, and some Salamanders. The 

 chondrocranium is invested by paired parietals, frontals, prefrontals, nasals 

 (absent in Siren and Proteus], paired vomers and a parasphenoid. The 

 Anura have a paired fronto-parietal, sometimes united medianly, nasals, 

 vomers and a parasphenoid. The vomer is single in Dactylethra, absent 

 in Pipa and Hylaplesia. The palato-pterygoid of Urodela appears as a 

 continuous membrane-bone subsequently divided, except in Proteus and 

 Menobranchus, into palatine and pterygoid bones the former becoming 

 continuous with the vomer of its side. The latter is absent in Siren. The 

 cartilage element appears later : the palatal element from the ethmoid, the 

 pterygoidal from the quadrate. The palato-pterygoid of Anura arises in 

 continuity with Meckel's arch, fuses with the ethmoid anteriorly and 

 remains in continuity with the quadrate posteriorly. Ossification takes 

 place from the perichondrium. The palatine is sometimes absent, some- 

 times subdivided. Two praemaxillae are always present, fused into one, 

 however in some Salamandrina. Maxillae are absent in Proteus, very 

 rudimentary in Siren and Menobranchtis. A quadrato-jugal, absent in all 

 Urodela, unites them to the quadrate or suspensorium in Anura with few 

 exceptions. The quadrate is more or less ossified in Urodela, and united 

 to the cranium by three processes. It is as a rule cartilaginous in Anura 

 and is united to the auditory capsule by an otic process, and articulated to 

 it by a pedicle. A squamosal lies on its external aspect. The lower jaw 

 is a persistent Meckel's arch. In Urodela it is invested by a dentary, 

 splenial and articular bone. A splenial is absent in Anura, most of which 

 have a pair of ossified lower labials ( = Mento-Meckelians)at the symphysis. 

 The extent of the gape of the mouth depends on the inclination of the 



1 Cope states that the Permian Trimerorhachis has but one condyle (American Naturalist, xviii. 

 1884). 



