SCOKPIONS OF THE GENUS ISOMETETJS. 441 



the base bearing a distinct lobe, on tbe distal side of which is a 

 distinct sinuation, the opposite (external superior) surface being 

 convex to correspond with tlie sinuation ; the movable digit 

 sinuate and lobate to correspond with the lobe and sinuation of 

 the immovable digit. 



Legs strongly granular and costate ; tihicB of two posterior 

 pairs armed distally with a spur. 



Pectines long, projecting beyond the fourth cosse, furnished 

 with 19 similar teeth. 



Measureme7its in millimetres. — Total length 43, tail 28; 1st 

 segment, length 3, width 3*5 ; 2nd, length 4, width 3 ; 3rd, length 

 4"3 ; 4th, length 5 ; 5th, length 7, width 3 ; vesicle, length 3"5, 

 width 2, height 2. Palp — humerus, length 5 ; brachium, length 

 5-5, width 2 ; manus, width 2*5, length of "hand-back" 3'5 ; 

 movable digit, length 5 '7. 



A single male specimen from Port Essington on the N. coast 

 of Australia, from Dr. Richardson's collection*. 



This species is related to I. variatus, Thorell. The male of this 

 last-named form is described and figured in Count Keyserling's 

 ' Arachniden Australiens — Scorpiones,' pp. 9-11, and figured, 

 as also is the female, on pi. i. An examination of this figure 

 shows clearly the points of difference between the two species. 

 Thus in /. variatus each of the four anterior caudal segments is 

 provided with a tooth, and the teeth are approximately equal in 

 size, whereas in I. armatus the second, third, and fourth only are 

 dentate and the tooth of the third is considerably larger than the 

 others ; again, in I. variatus there is no sinuation in the digits 

 such as is met with in /. armatus, and the manus is not wider than 

 the brachium ; the manus with its dactyli, too, is much shorter, 

 being only slightly longer than the first two caudal segments, 

 whilst in I. armatus it is almost as long as the first two and half 

 the third. 



ISOMETEIJS SERBATUS, Sp. U. (PL XI. figS. 4-4 h.) 



Colour (dry specimen) : prevailing colour ochraceous or fulvous, 

 variegated with black ; ocular tubercle black ; anteocular area of 

 cephalothorax infuscate ; tergites mostly ochraceous, each, except 

 the last, marked posteriorly with a lateral fuscous spot on each 



* Since the above was written, I have come across a female specimen of this 

 species, and have figured it on PI. XI. fig. 3. It differs from the male in that 

 the hand and dactyli are of normal form and the candal spines much smaller. 



