THE PRESENT DISTRIBUTION OF THE ONYCHOPHORA, 



A GROUP OF TERRESTRIAL INVERTEBRATES. 



By AUSTIN H. CLARK 



CONTENTS 



Preface I 



The onychophores apparently an ancient type 2 



The physical and ecological distribution of the onychophores 2 



The thermal distribution of the onychophores 3 



General features of the distribution of the onychophores 3 



The distribution of the Peripatidae 5 



Explanation of the distribution of the Peripatidae 5 



The distribution of the American species of the Peripatidae 13 



The distribution of the Peripatopsidae 17 



The distribution of the species, genera and higher groups of the ony- 

 chophores in detail 20 



PREFACE 



A close study of the geographical distribution of almost any class 

 of animals emphasizes certain features which are obscured, or some- 

 times entirely masked, in the geographical distribution of other types, 

 and it is therefore essential, if we would lay a firm foundation for 

 zoogeographical generalizations, that the details of the distribution 

 of all types should be carefully examined. 



Not only do the different classes of animals vary in the details of 

 their relationships to the present land masses and their subdivisions, 

 but great diversity is often found between families of the same order, 

 and even between genera of the same family. Particularly is this 

 true of nocturnal as contrasted with related diurnal types. 



As a group the onychophores have been strangely neglected by 

 zoologists. Owing to their retiring habits they are difficult to find, 

 and few collectors have devoted their attention particularly to them. 

 Thus the majority of the species are known from very few specimens, 

 which often were collected more or less accidentally. For instance 

 the original examples upon which the Rev. Lansdown Guilding based 

 the name Peripatus juliformis, creating for the new form the class 

 Polypoda in the phylum Mollusca, were collected by him in St. Vin- 

 cent in 1825 ; only once since have specimens of this species been 



Smithsonian Miscellaneous Collections, Vol. 65, No. 1 



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