12 G. A. BOULENGER 



8. JMaTbixia IxildLelbraiidLtii , Peters. 



Numerous specimens. Obbia, and route from Obbia to Ber- 

 bera. 



The anterior loreal is not always in contact with the first 

 labial. The three bluish-grey dorsal stripes and the black spots 

 or cross-bands between them usually disappear in the adult , 

 some of which are nevertheless very handsome owing to three 

 large deep black spots on each side of the neck , relieved by 

 smaller white spots between and below them ; the top of the 

 head may be speckled with black and the chin and throat may 

 bear scattered deep black spots. The largest specimen measures 

 77 millim, from snout to vent. 



9. 01xalcid.es ocellatus, Forsk. 



Five specimens. Route from Obbia to Berbera. 



These specimens belong to the typical form ; four have 28 

 scales round the body, the fifth has only 26, thus filling up 

 the gap, so far as the number of scales is concerned, between 

 the typical form and the var. ragazzii (Bouleng. Ann. & Mag. 

 N. H. [6] V. 1890, p. 444), as may be seen from the following 

 table : 



1. var. ragazzii (Assab) 24 scales 



2. forma typica (Sahara and N. E. Africa) . . 26-30 » 



3. var. tiligugu (N. Africa East of Morocco) . 28-34 » 



4. var. vittatus (Tangier) . . . . . . . . 30-34 » 



5. var. polylepis (Plain of Morocco) .... 34-40 » 



The interest of such a series of forms, overlapping each other, 

 so to speak, and agreeing in their succession so closely with the 

 chain of districts inhabited by them, is very great, and affords 

 one of the best examples I know of derivation of forms. 



