TAXONOMY AND DISTRIBUTION 



57 



sixteen in the Pacific; it was also found off Easter Island. 

 The stations are as follows: one (19) in the Sargasso Sea, 

 three (47, 78, 80) in the Galapagos region, eight (48, 81, 82, 

 83, 84, 85, 95, 96) in the region of South Pacific island fields, 

 two (61, 65) in the South Pacific middle latitudes, and three 

 (107, 139, 140) in the North Pacific trade region. 



There are 16 pump and 16 net samples, of which 9 were 

 taken at the surface, 16 at 50 meters, and 7 at 100 meters. 

 Maximum frequency, 31 per cent at station 78; other records 

 above minimum (2 to 14 per cent) from stations 47, 48, 61, 

 80, 81, 82, 85, 95, 139; average in Pacific net samples, 7.7 

 per cent. 



Temperature: Atlantic, net sample 22?42; Pacific, pump 

 samples 23?88-29?34 (2f>?33), net samples io?92-28?74 

 (24^49). Salinity: Atlantic, net sample 37.05; Pacific, pump 

 samples 34.39-36.49 (35.74), net samples 34.05-36.49 (35.74). 

 Density: Atlantic, net sample 25.67; Pacific, pump samples 

 21.90-25. 11 (23.49), net samples 22.43-26.06 (23.91). pH: 

 Atlantic, net sample 8.25; Pacific, pump samples 8.14-8.39 

 (8.21), net samples 8.03-8.39 (8.21). 



Rhabdonella cornucopia Kofoid and Campbell 



Rhabdonella cornucopia Kofoid and Campbell, 1929, p. 215. 

 fig- 399- 



The short lorica, with high oral rim, conical bowl, feeble 

 ribs, and conical aboral horn, has a length of 2.22 oral diam- 

 eters. The oral rim is erect, high, and ringlike, and the sub- 

 oral trough is flat; the diameter of the outer margin of the 

 latter is 1.22 oral diameters. There is almost no suboral 

 flare. The bowl is conical (18 increasing to 30 in the 

 lower part) and at its lower end gives rise to the aboral horn. 

 The horn is 0.55 oral diameter in length, conical (12 ), 

 truncated at the tip, and minutely open. 



The wall is subuniformly 0.15 oral diameter in thickness. 

 There are thin laminae and enclosed faint alveoles. The 

 ribs number 26, and are very faint and difficult to follow, and 

 left-twisted (hardly io°); there are no fenestrae. The horn 

 is lemon yellow. 



Length, 97 to 146(1. 



Rhabdonella cornucopia is longer than R. cxilis, and has 

 faint ribs and a longer conical horn. Rhabdonella amor 

 lacks a horn and has distinct ribs. The remaining species 

 are altogether different. 



Recorded from two stations in the Pacific, as follows: one 

 (60-61) in the South Pacific middle latitudes, and one (144) 

 in the North Pacific middle latitudes. 



There are 1 pump and 1 net sample, both taken at the 

 surface. Frequency, minimum. 



Temperature, net sample, 23^26; salinity, 34.97; density, 

 23.86; pH, 8.37; all records at station 144. 



Rhabdonella cuspidata (Zacharias) Brandt 



Rhabdonella cuspidata, Kofoid and Campbell, 1929, p. 215, rig. 

 4'7- 



The greatly elongated lorica, with contraction and later 

 inflation and conical horn, has a length of 7.0 oral diameters. 

 The oral rim is low, ringlike, and submerged by the higher 



outer margin of the concave suboral trough; the diameter of 

 this margin is 1. 17 oral diameters. The bowl contracts (10°) 

 for 1.33 oral diameters, basing .11 the lower end a diameter 

 of 0.9 oral diameter, and then expands, reaching 1.0 oral 

 diameter at 0.46 total length below the rim. The lower bowl 

 is convex conical (30 ) within [.5 oral diameters. At its 

 lower end is the narrow conical (8 ) aboral horn, the 

 length ol which is nearly 0.36 total length; its free tip is 

 sharp. 



The wall has a thickness of 0.1 oral diameter across the 

 suboral trough and becomes reduced to a third of that in 

 the bowl. There are thin laminae which enclose several 

 layers of small alveoles, and the fenestrae cut across from 

 lamina to lamina. There are approximately 30 subvertical, 

 sometimes branched ribs. The intercostae have 12 to 30 

 very minute, oval, faint fenestrae. 



Length, 421U. 



Many loricae are much shorter (down to 250(1) than 

 usual. 



Rhabdonella cuspidata, with its lateral concavity and swell- 

 ing and its great length, is easily distinguished from other 

 species. In elongation and proportions it approaches R. 

 conica, but it is otherwise only remotely like that species. 



Recorded from one station (65) in the South Pacific middle 

 latitudes, in a net sample taken at the surface. Frequency, 

 8 per cent. 



Temperature, 2o?22; salinity, 34.53; density, 24.37; pH, 

 8.10. 



Rhabdonella elegans Jorgensen emended Kofoid 

 and Campbell 



Rhabdonella elegans, Kofoid and Campbell, 1929, p. 215, fig. 

 401. 



The rather short lorica, with wide, generally conical bowl 

 and tapering horn, has a length of 2.81 oral diameters. The 

 oral rim is relatively high, with outward-sloping sides. The 

 suboral trough is deep and subangular; the diameter of its 

 outer margin is 1.17 oral diameters. There is a distinct flare 

 (62°) well within the anterior 0.5 oral diameter. The 

 diameter of the bowl at the lower end of the flare is 1.0 oral 

 diameter. Below this level the bowl is decidedly convex 

 conical (io° increasing to 42 in the lower half). The aboral 

 horn is narrow conical (12 ), and 0.82 oral diameter in 

 length; it has a sharply pointed free tip. 



The wall has a thickness of 0.06 oral diameter in the bowl 

 and has very little suboral thickening. There are thin 

 laminae which enclose fine primary alveoles in several layers. 

 There are approximately 24 vertical, unbranched ribs run- 

 ning from end to end. Fenestrae are lacking. 



Length, no to 122U. 



Rhabdonella elegans differs from R. cornucopia in its 

 longer horn and more convex bowl. It has a horn, which is 

 lacking in R. amor, and the horn is longer than that of R. 

 indica. It is much longer and more convex than R. exilis. 



Recorded from one station (14) in the Gulf Stream, in a 

 net sample taken at 100 meters. Frequency, minimum. 



Temperature, i4?02; salinity, 35.59; density, 26.66; pH, 

 8.06. 



