138 DISCOVERY REPORTS 



of the test. No visible apertures ; a series of coarse perforations sometimes found on the 

 extremity of the final chamber appears to be superficial. Sutural lines depressed, the 

 marginal edge of each chamber slightly overlaps the previous chamber, giving the ap- 

 pearance of a covered canal, but none can be traced in transparent mounts. 



This is the commonest species in the Mediterranean and is well illustrated by Side- 

 bottom, whose figures show the overlapping of the sutural edges and the sieve-like 

 perforations. It is like all the Delosinae very variable, but bears a general resemblance 

 to a Bidimina of the group of B. pyrida — B. affinis. Its range probably extends to the 

 Indo-Pacific region, as the first figure in the Kerimba monograph (tit supra) almost 

 certainly represents this species. Unfortunately the Kerimba specimens have been 

 ruined by damp, so it is impossible to confirm the identity. 



Delosina complexa is extremely rare in the Antarctic, two specimens were found at 

 St. 175 in the Bransfield Strait, and another at St. 181 in the Palmer Archipelago. 

 Wiesner also found it at Kaiser Wilhelm's Land. The specimens are all of the average size 

 of the Delos types, and very small compared with the local species D. sutilis. They show 

 no signs of the "stitches" in the sutures which mark that species. The largest specimen 

 is 0-45 mm. long and 0-25 mm. broad. 



263. Delosina complanata, sp.n. (F293). 



Polymorphina complexa, Sidebottom, 1904, etc., RFD, 1907, p. 16, pi. iv, figs. 4, 8, (.') 9. 

 Polymorphina complexa, Heron-Allen and Earland, 1916, FSC, p. 48, pi. viii, figs. 5-7. 

 Polymorphina complexa, Heron-Allen and Earland, 1932, F, No. 293. 



The general characters of the species are similar to those of D. complexa, but the 

 chambers which are at first triserial rapidly become biserial and opposed, giving a com- 

 pressed appearance to the test. The ratio of length to breadth varies greatly in different 

 specimens, in some instances the last pair of chambers embraces quite four-fifths of the 

 entire test, giving a quadrate appearance to the specimen. Sidebottom's fig. 8 illustrates 

 an extreme instance of this form, but he does not figure the other extreme of variation 

 in which the test is elongate with almost parallel sides. I think his fig. 9 represents an 

 abnormal specimen of this species. In general appearance the test resembles a Poly- 

 morphina of the group of P. ligua (= P. compressa), and is equally variable. 



In the Mediterranean the species occurs with Delosina complexa, and with about equal 

 frequency or rarity, for specimens are always uncommon. A single excellent specimen 

 from South Cornwall, and the Discovery specimens (F 293) from off Cape Horn which 

 are all referable to D. complanata, show that the species has a wide range, but so far it 

 has not been found in the Antarctic. 



264. Delosina polymorphinoides, sp.n. 



Polymorphina complexa, Sidebottom, 1904, etc., RFD, 1907, p. 16, pi. iv, figs. 5-7 and text- 

 fig- 7- 



} Polymorphina complexa, Heron-Allen and Earland, 1914, etc., FKA, 1915, p. 673, pi. li, 

 figs. 2, 3. 

 Polymorphina complexa, Sidebottom, 1918, FECA, p. 145, pi. v, figs. 13, 14. 



The general characters of the species are those of D. complexa, but the chambers are 



