188 
Spelerpes. 
Of this genus six species have been examined, counting those 
previously described, all being without vestige of lungs or larynx. 
Of these, Spelerpes porphyriticus which is the largest lungless form 
thus far observed, was used for the dissection,-and Spelerpes bilineatus 
for the serial sections. The other were simply cut opened and 
examined for lungs. As the limit of size must be soon reached, within 
which integumental and pharyngeal respiration is sufficient, the con- | 
siderable dimensions of 8. porphyriticus may excite some surprise. 
The following measurements were made upon the specimen used for 
the dissection given in Fig. 6. 
| Total length 164 mm 
Nose to fore limb 20. 
Fore limb to hind limb 64 „ 
Hind limb to tip of tail Lowes 
Girth of body (middle) 4 ,, 
Girth at cloaca — 1) ee 
As this seems a rare species, I cannot say how much larger some 
specimens may be, but do not think that this is the maximum size. 
Comparing it anatomically with Plethodon it will be seen that 
the two muscles, digastricus pharyngis and dorso-laryngeus 
are no longer distinct at their insertion, but participate in the formation 
of a pharyngeal sheet of transverse fibres, which meet anteriorly in 
the middle line, but posteriorly are inserted into the pericardium. 
At their origins the two muscles are distinct. The digastricus 
pharyngis arises as usual from the outer surface of the otic cap- 
sule, but the dorso-laryngeus is reduced to an extremely fine 
band of two or three fibres. In the series (S. bilineatus) this is so 
fine that it is included in about three sections of 20 u each, but 
arises from the dorsal integument in the normal way. 
Below the pharyngeal sheet formed by these two muscles, there 
begins another, formed in part by fibres from the ventral margin of 
the scapula (= scapulo-pharyngis of Plethodon) and partly by 
fibres proceeding from the more undifferentiated dorsal trunk muscles. 
This does not seem as well developed in S. bilineatus and is pro- 
bably not as much needed as in the larger form. Of the scanty 
fibres covering the ventral wall of the pharynx in Plethodon there is 
not a trace. The whole impression gained by the study of this region 
in Spelerpes is that there is a distinct tendency to forma 
transverse pharyngo-oesophageal sheet, employing for 
this the laryngo-tracheal muscles which thus gradu- 
ally lose their separate identity. Such a sheet must bear 
