232 MR. w. K. PARKER ON THE STRUCTURE AND 



The vomers (v.) are very small shells, bilid behind, and protecting the circular inner 

 nostrils (in.), whicli are v?ide apart. 



Very much of what is peculiar in this skull may be summed up in the word 

 "arrested ;" but to this general character must be added such things as are not often 

 seen even in young specimens of higher kinds : — 



1 . There is a small basioccipital, and a persistent cranial notochord. 



2. The prootics and ex-occipitals are continuous on the same side. 



3. There are no secondary fontanelles. 



4. The optic feiiestra is very large. 



5. The girdle-bone is arrested, and there are three rudiments answering to the 

 lateral and perpendicular ethmoids. 



6. The palato-suspensorial arch goes no further back than the postorbitul region. 



7. The pedicle is not absorbed above. 



8. The palatine bone is a mere thread. 



9. The Eustachian opening is nearly closed. 



10. There is only a Hgulate, imperfect annulus. 



11. There is no columella. 



12. The mento-Meckelian rods and the condyles of the mandible are very large. 



13. The hyo-branchial plate has its processes feebly developed, as in a young 

 Common Frog or Toad. 



I shall take the liberty to modify Dr. Gunther's classification, somewhat; but I see 

 no advantage in bundling together several of these groups — as Professor MlVART has 

 done (Proc. Zool. See, 1869, p. 289). 



Diplopelma might go with Engystoma and help to fonn the " Engystomidse." 

 Dr. GuNTHER himself (" Bat. Sal.," p. 50) says that in Diplopelma the toes are only 

 "one-third webbed," and in Engijstoma free (p. 51). Moreover, the columella is well 

 developed in both these genera, whereas in Rhinoderma it is a mere rudiment. The 

 author says of another member of his " Rhinodermatidse," viz. : Atclopus, " I have 

 never seen the animal" (note to p. 48), and of another genus — Uperodon — that "the 

 tympanum is hidden;" and his description of the skull (p. 49), although short, is 

 enough to show that it is very similar to that of Hijlaplesia, and extremely unlike 

 that of either Ehinoderma, or of the species of Diplopelma, or that of Engystoma, 

 soon to be described. 



By their skulls these small species must be judged, not keeping out of sight other 

 characters, especially the suppression of the clavicida ("pro-coracoid"), and of the 

 manubrium sterni {"omosternum")."" 



I shall follow Dr. Gunther's example and limit the next group to the one genus 

 Phryniscus (see " Bat. Sal.," p. 42). 



* These pro-coracoitls aud omosttiuums ;iro absent in Engystoma, Callula, autl l)i2>l"j^>flma (Mivabt, 

 Proc. Zool. Soc, 18G;t, p. 289). 



