571 



A. similis A. bispinosus 



1 . Distal process of 5th segment 1 . Distal process of 5th segment 

 of pereopods II reaches only of pereopods II reaches tip of 

 2/3 length of 6th segment. denticle of 6th segment. 



2. Inner process of coxal plate V 2. Inner process of coxal plate 

 rounded. pointed. 



3. In pereopods V, 2nd segment 3. In pereopods V, 2nd segment 

 barely shorter than distal 2/3 length of distal segments, 

 segments. 



4. Telson galeiform, with stret- 4. Telson triangular, with 

 ched tip. pointed tip. 



5. Telson almost twice as long as 5. Telson only slightly longer 

 last urosomite. than last urosomite. 



The above differences permit us to consider A. similis an indepen- 

 dent species. 



Distribution: Known from the Atlantic Ocean (south of 38° N) and 

 the Mediterranean and Red seas. It lives in the 0-200 m layer. 



Absent in our collections. 



461 3. Amphithyrus muratus Volkov, sp.n. (Fig. 248) 



The type specimen is preserved in the Pacific Ocean Scientific 

 Research Institute of Fisheries and Oceanography (TINRO). 



Length of adults up to 3.5 mm. 



The body is identical in shape to A. similis. All the somites of the 

 body, the telson and the 2nd segment of the pereopods are covered with 

 a reticulate sculpture. The 2nd segment of pereopods VI has grooved 

 sculpturing in the central part and a reticulate pattern along the periphery. 



The 2nd segment of pereopods I has barely bulged margins and is 

 only slightly longer than the distal segments together; the 4th segment 

 is not broader than the 5th; the 5th segment has a short distal pro- 

 cess and bears a few submarginal spines along its posterior margin. The 

 2nd segment of pereopods II is much longer than the distal segments 

 together; the 4th segment has bulged margins and is broader than the 

 5th; in the 5th segment the distal process falls short of the base of the 

 denticle on the posterior margin of the 6th segment and the posterior 

 margin of the segment bears fine submarginal spines. Coxal plate V has 

 an inner projection with a rounded tip and a denticulate lower margin. 

 The 2nd segment of pereopods V is 2.1-2.2 times longer than wide; the 

 distal segments together are approximately as long as the 2nd segment. 

 The 2nd segment of pereopods VI is similar to that in A. similis but its 



462 length only 1.4 times the width versus almost twice in A. similis; the 

 shape and size of the lateral fissure are almost the same as in A. similis 

 and A. bispinosus; the 4th segment is long, with parallel margins and a 



