1«^ 



in 



ii 



\m \ 



310 BULLETIN 34, UNITED STATES NATIONAL MUSEUM. 



fontanelle and with complete ethmoid arcli, and a styloid osseous xiplii- 

 sternum, with termina' "irtilagiuous disk ; tlie auditory organs perfectly 

 developed; the lowes 'eveloped ethmoid arch and frontoparietal 



roof, and disciform c. ginous xii)histerimm without style, with 

 Eustachian tubes ami memhrauum tympani wanting. Accompanying 

 this succession, we have four modiOcations of the family structure to 

 adapt to as many modes of life: the aquatic, the terrestrial, the arbo- 

 real, ami the subterranean. As the earth's surface is the common 

 ntediiim between the above extiemes, so the s])ecies of terrestrial habits 

 furnish us with none of the adaptive extremes of structure, but reujiiin 

 an intermediate grouj), from which the succession of structures, inter 

 rupted, it is true, passes towards the divergent types. Develojuneiiral 

 structures accompany and confirm the adaptive, but by no means al- 

 ways coincide. 



The aquatic habit is attained when the digits behind iirc not only 

 webbed, but when the external metiitarsi are separated by Mu'inbiane 

 also; the arboreal, when the terminal phalanges are furnished witli a 

 terminal transverse limb, which supi)orts an adhesive disk. Tlse sub 

 terranean is shortened, and furnished with a great development of tin' 

 lirst digit or prepollex of the tarsus, which is covered by a corneous 

 sheath, and serves as a si)ade. The lirst type may be combined with 

 the third, as in Mixophyes and Chiroleptes, or either may be furnished 

 with a bony overioohng of the temporal muscles, and pciietration of its 

 integuments by the hyperossilication of the cranium. 



The fossorial spur is weak in lleliopoius and Paludicola, weaker in 

 Mitrolysis, and just represented in Ceratophiys. The palmate foot is 

 <liminished in Calyi)tocei>iialus, reduced in Mixophyes and Chirolei»tes, 

 and represented by a trace in ll^loriiiiia and Limnoinedusa. The un- 

 developed ear is seen in Telmatobius and in Alsodcs. 



Tiie variations in tiie develtti»inent of the tliumb are not so striking 

 as in the llylida'. In (inatiiophysa, Cystignathus, and Ceratophrys 

 the trapezium sui»ports an osseous metacarpal and obtuse phalange, 

 whi(di are concealed ill a large tiiln'icle. In Mixophyes, on the otiier 

 hand, the inetacai|)al is slender, cut irely caitiiagiiious, and does not 

 support a phalange. Tiiere is no where a spur, as in Ilypsiboas. 



With regard to the deiinal attaciiments, the following inii)ortant 

 varieties o(!cur; in the family generally, but especially among Ilylodes 

 and ('ystignathi, the dorsolateral septum is placed esi»ecially high up: 



I'seudea. — Se[)ta in Pseiidis as in Ifaiia; in Lysajuis tlu^ laterovenlral 

 line is a little widened. In Mi.ropln/cs ftisriohifus the lateroventrals 

 are very wide, and leave the ventral free space very narrow behind the 

 middle. 



(Jemtophryiks. — In Ceratophrys the lateral septa nvo narrow, and 

 there are two posterior abdominal transverse septa, similar <o tliost* 

 altiiched to the sternum. In Crrdtophri/s urntUa these are wanting, luit 

 the dorsolateral line is veiv broad. 



