TAXONOMY AND DISTRIBUTION 



6i 



and horn, subequal in length, has a length of 5.5 oral diam- 

 eters. The oral rim is erect, ringlike, and about as high as 

 the outer rim of the suboral trough. The suboral trough is 

 concave and the diameter of its outer margin is 1.2 oral 

 diameters. The bowl flares (38°) within the upper o.i oral 

 diameter. It then tapers (14°) for 0.42 total length, then 

 becomes subconical (28°) for 0.18. From its lower end 

 arises the aboral horn. The horn tapers (7°) and has a 

 length of 0.4 total length, and its free tip is sharp. 



The wall has a thickness of not over o.i oral diameter 

 across the trough, and thins regularly below. There are thin 

 laminae which enclose several layers of minute alveoles. 

 There are 42 sometimes branched, anastomosed, subvertical 

 ribs, which continue from end to end. Between the ribs are 

 12 to 20 small, scattered circular fenestrae, mostly gathered 

 in the upper bowl and more rare below. 



Length, 26op. 



That part of Hofker's material which has distal knobs is 

 assigned in this report to Rhabdonellopsis triton. Marshall 

 does not distinguished spiralis from related species, but since 

 only one figure is clearly of this species, this Barrier Reef 

 material is all included as spiralis. One of Marshall's figures 

 (fig. 27) strongly suggests Rhabdonella unadyomene, save 

 that the ribs are reversed and the oral rim more developed; 

 this lorica may, however, be only an incomplete (abnormal 

 or defective.?) specimen. It is not at all like the imperfect 

 R. hydria, which is probably only a defective spiralis. Defec- 

 tive loricae were not encountered in the Carnegie material 

 save at station i, where at 70 meters one specimen somewhat 

 like Marshall's was found. On the whole it is rather re- 

 markable that so few defective loricae of these ciliates are 

 found, considering their abundance in the ocean. Perhaps 

 this is because they are quickly formed. 



Rhabdonella spiralis is closest to R. valdestriata, R. striata, 

 and R. hebe. It is usually longer than these, with more 

 slender proportions, with distinct suboral flare, and with 

 subequal upper bowl and horn. There is more transition 

 between lower bowl and horn than in hebe or valdestriata, 

 but not so much as in striata. It never has the length, nar- 

 rowness, or facies of R. conica. The remaining species are 

 clearly unlike it and occasion no opportunity for confusion. 



Recorded from forty-four stations, sixteen in the Atlantic 

 and twenty-eight in the Pacific, as follows: three (i, 15, 16) 

 in the Gulf Stream, four (17, 18, ig, 21) in the Sargasso Sea, 

 five (24, 26, 27, 29, 30) in the Atlantic equatorial region, 

 four (31, 32, 33, 34) in the Caribbean Sea, two (35, 37) in 

 the Pacific equatorial region, eight (45, 46, 47, 68, 69, 78, 79, 

 80) in the Galapagos region, six (48, 87, 89, 90, 95, 97) in 

 the region of South Pacific island fields, nine (50, 51, 53, 54, 

 61, 62, 62-63, '^4' 65) in the South Pacific middle latitudes, 

 two (131, 146) in the California region, and one (145) in 

 the North Pacific middle latitudes. 



There are 46 pump and 27 net samples, of which 31 were 

 taken at the surface, 24 at 50 meters, i at 70 meters, and 17 

 at 100 meters. The preference of this species for surface 

 water is evident. Maximum frequency, 90 per cent at station 

 64; other records above minimum (2 to 88 per cent) from 

 stations 18, 30, 31, 54, 61, 62-63, 65, 145; average in net 



samples, Atlantic 1.6 per cent. Pacific 37.5 per cent; in pump 

 samples, 300 loricae -counted at station 15; other pump 

 records i to 43, average in the Pacific 6.0. 



Temperature: Atlantic, pump samples i8?40-28?5i (25?76), 

 net samples i5?55-28?05 (22^28); Pacific, i3?28-28'?74 

 (22?7o) and io?92-24?38 (i8?5o), respectively. Salinity: 

 Adantic, pump samples 29.70-36.58 (35.80), net samples 

 35.6r-37.15 (36.45); Pacific, 31.68-36.44 (35.27) and 33.36- 

 36.03 (34.59), respectively. Density: Atlantic, pump samples 

 18.62-26.01 (23.69), net samples 23.20-26.34 (25.00); Pacific, 

 20.20-25.40 (24.15) and 24.24-26.06 (24.58), respectively. 

 pH: Atlantic, pump samples 8.11-8.31 (8.26), net samples 

 7.96-8.37 (8.29); Pacific, 8.05-8.28 (8.17) and 8.03-8.34 

 (8.17), respectively. 



Rhabdonella striata (Biedermann) Brandt emended Kofoid 

 and Campbell 



Rhabdonella striata, Kofoid and Campbell, 1929, p. 219, fig. 

 411. 



The moderately tall lorica, with stout conical bowl and 

 elongate conical horn, has a length of 3.71 oral diameters. 

 The oral rim is a low, outward-recurved rim, which projects 

 a little above the outer margin of the suboral trough. The 

 suboral trough is flattened concave; the diameter of its outer 

 margin is 1.09 oral diameters. There is a wide suboral flare 

 (60°) within the upper 0.1 oral diameter. The upper bowl 

 tapers (16°) for 0.42 total length, and then becomes sub- 

 conical (44°) for 0.19 total length. The aboral horn is 

 narrow concave conical (5°), with a length of 0.39 total 

 length and with a truncated free tip. 



The wall has a maximum thickness of approximately 0.1 

 oral diameter. There are thin laminae which enclose fine 

 alveoles in several layers. There are 42 commonly branched, 

 anastomosed, subvertical, low ribs which continue from end 

 to end. Fenestrae are numerous, but small and not espe- 

 cially conspicuous. 



Length, 2251.1. 



Rhabdonella striata has a more sharply differentiated lower 

 bowl and more ribs than R. valdestriata. It is stouter and 

 shorter, and has more ribs than R. spiralis. Rhabdonella 

 brandti is shorter. 



Recorded from fifty-five stations, sixteen in the Atlantic 

 and thirty-nine in the Pacific, as follows: three (20, 20-21, 

 21) in the Sargasso Sea, nine (22, 23, 24, 25, 26, 27, 28, 29, 

 30) in the Atlantic equatorial region, four (31, 32, 33, 34) in 

 the Caribbean Sea, six (52, 56, 63, 65, 66, 67) in the South 

 Pacific middle latitudes, three (68, 69, 80) in the Galapagos 

 region, seven (89, 90, 93, 95, 96, 97, 159) in the region of 

 South Pacific island fields, four (99, 152, 153, 154) in the 

 Pacific equatorial region, six (100, 107, 108, 109, no, 138) 

 in the North Pacific trade region, eight (132, 133, 135, 136, 

 137, 146, 148, 149) in the California region, and five (141, 

 142, 143, 144, 145) in the North Pacific middle latitudes. 

 Rhabdonella striata is the most common Rhabdonella in the 

 ocean and is most widely distributed in warmer seas. 



There are 54 pump and 45 net samples, of which 37 were 

 taken at the surface, 24 at 50 meters, and 38 at 100 meters. 



