390 MR. R. I. POCOCK ON THE [ Apr. 21, 
within the limits of the Mygalomorphe. This conclusion as to 
their descent is supported by the fact that the specialised arrange- 
ment of the eyes is foreshadowed in Dyareyops, one of the 
Nemesize, and by the presence of a single row of ungual pectinations 
in the Aganippz and all the Australian Nemesize, two such rows 
being characteristic at least of the southern forms of the Cyrt- 
auchenil. 
The Aporoptychi are specialised Cyrtauchenii. Their distri- 
bution suggests that they originated in South America or South 
Africa, and crossed from the one continent to the other when the 
two were united. This conclusion is strongly supported by the 
occurrence of two of the genera in both of the areas in question. 
Family Crenizip&. 
The genera of the subfamily Ctenizine are almost exclusively 
northern. Cteniza, Hpycephalus, and Cyrtocarenwm are restricted 
to the Mediterranean; Sterrhochrotus occurs in Turkestan ; 
Latouchia 11 China and the Himalayas; Pachylomerus in Spain, 
Algeria, Japan, N., Central, and 8. America, and the West Indies ; 
Bothriocyrtwm in California; Conothele ranges from Burma to the 
Solomon Islands. The only genus which is exclusively southern 
is Stasimopus, which is confined to 8. Africa. 
The structural features of this group suggest that it is a 
specialised offshoot from some northern forms of the Cyrtau- 
cheniide. This conclusion is borne out by the more restricted 
distribution of the genera, which, in virtue of their later appearance 
in the Northern hemisphere, have had less time to distribute 
themselves over the southern continents. The only genus which 
has entered the Ethiopian Region, namely Stasimopus, appears to 
have done so not earlier than the Pliocene, since it is seemingly not 
represented in Madagascar. Conothele, too, seems to have 
migrated southwards by way of Burma to the Solomon Islands, 
after the separation of Australia; Pachylomerus, the only form 
which enters the Neotropical Region, appears almost certainly to 
be a northern immigrant from the Sonoran region, 
The Idiopine section, apparently a specialised offshoot of the 
Ctenizine, has, on the contrary, a more southern distribution 
than the typical Ctenizine. The genus /diops (Acanthodon) itself 
has representatives in Central Asia, Syria, Arabia, India and 
Burma, Tropical and South Africa, and 8. America ; Heligmomerus 
occurs in India, Ceylon, and Tropical Africa; Gorgyrella in 
S. Africa; while the aberrant Pseudidiops is confined to the 
forests of South America. 
The presence of the genus /diops so far north as Central Asia 
and Syria, and in India, Burma, Tropical and Southern Africa, 
and Brazil, attesting as it does considerable powers of adaptation 
to varied climatic and other physical conditions, justifies the 
supposition that the genus never formed part of the Sonoran 
fauna of America. Otherwise it would be difficult to account for 
