432 IIARP.IS HAWTHORNE WILDER ON 



from the ril) previous to the sacral rih to the dorsal end of the ilium; aud in one of these 

 which 1 have had the opportunity of examining more closely, tlie sacral rih on the right 

 is normal and attached to what is probahly the 19tli vertebra, while the sacral rib upon 

 the left side proceeds from the next posterior vertebra (20th) . In addition to this, a 

 strong but narrow ligament proceeds from the free end of the previous rib (19th) and 

 inserts upon the dorsal end of the iliinn anterior to the attachment of the sacral rib. 

 As this fragment came from a student's preparation, the remainder of which had been 

 lost, the exact determination of the vertebrae cannot l)e made, but judging from the 

 other cases of oblique attachment which have been reported, the numbering is undoubt- 

 edly as given. Tliis case resolves itself into one of "oblique attachment," such as have 

 been reported by G. H. Parker, Waite, and Bumpus, the obli({uity being dextro-sinistral 

 (see above, under Vertebral Column) . 



The Free Limbs. 



The serial homology between the fore and hind limbs in Necturus is very striking, 

 aud in so primitive an animal, perhaps the most primitive one possessing a cheiropte- 

 rygium, points to a fundamental similarity of origin. It is thus of greater morphological 

 interest than correspondences in such modified structures as the paddles of Ichthyosaurus 

 vphere it is Ukely that the similarity is a secondary modification due to a similar method 

 of use. This resemblance, which is apparent externally, is still more emphasized by the 

 skeletal parts, and it seems incongruous to find such similar free limbs attached to such 

 different girdles. Each limb terminates in four digits, the lost member being generally 

 considered to be the first, and the phalangeal formula, 2-2-3-2, is the same in both 

 manus and pes.^ 



With the exception of carpus and tarsus, which are wholly cartilaginous, the limb 

 bones of the adult consist each of a hony shaft running through the middle, and two 

 cartilaginous epiphyses, a slight exception being the terminal phalanges which are without 

 epiphyses at the distal end. The shaft, or diaphysis, ossifies perichondrially, as always in 

 the Amphibia, and forms a tubular sheatli of bone, thick and constricted in the middle of 

 its length and tapering at the ends to thin edges, the whole mass being something like 

 the centrum of a biconcave vertebra considerably prolonged in the direction of its length. 

 The epiphyses always remain purely cartilaginous, and never obtain calcareous deposits as 

 in the frog. 



' On this point Cope ('89, p. 25-28) seems to liave made a singular mistake, giving the phalangeal foniuila for iV. 

 iiiamilatus as 1—3-3-2 for the manus, ami 1-2-2-2 for the pes. For the rare Carolina form, N. punctatus, he gives the 

 formula 2-2—3-2 for both limbs, which corresponds to the normal condition in N. maculatus and is undoubtedly character- 

 istic of the entire genus. 



