TAXONOMY AND DISTRIBUTION 



59 



The wall is thickest across the ridgelike suboral flare, 

 where it reaches 0.05 oral diameter; elsewhere it is decidedly 

 thinner. There are exceedingly thin, dark laminae with 

 numerous minute alveoles enclosed. A curtain-like film of 

 transparent jelly encloses the upper bowl. There are 18 

 vertical, frequently anastomosing, branching, rarely discon- 

 tinuous and short ribs, which run the whole length of the 

 lorica save suborally. There are 12 to 18 small fenestrae (the 

 sites of coccoliths), and fine alveoles form an external mesh- 

 work in the intercostae. The whole lorica is a deep brown 

 color. 



Length, 303H. 



The aboral horn of the figured specimen (fig. go) is not 

 so thick as usual. 



Rhabdonella hcnseni is stouter and plumper than any 

 species of the R. spiralis group. It is closest to R. torta and 

 R. lohmanni. It may be distinguished from lohmanni by the 

 vertical rather than oblique ribs, the smaller size, and the 

 more slender horn. From torta it may be distinguished by 

 the larger size and the vertical rather than right-spiral ribs. 



Recorded from three stations, one in the Atlantic and two 

 in the Pacific, as follows: one (17) in the Sargasso Sea, one 

 (96) in the region of South Pacific island fields, and one 

 (135) in the California region. 



There are 2 pump samples and i net sample, of which 2 

 were taken at the surface and i at 50 meters. Frequency, 

 minimum. 



Temperature: Adantic, net sample 2i?85; Pacific, pump 

 samples 23?76-29?3o (26^53). Salinity: Atlantic, net sample 

 36.60; Pacific, pump samples 35.12-35.27 (35.19). Density: 

 Atlantic, net sample 25.49; Pacific, pump samples 22.19-23. 83 

 (23.01). pH: Atlantic, net sample 8.27; Pacific, pump sam- 

 ples 8.23-8.37 (8.30). 



Rhabdonella indica Laackmann 

 RluibdoiicUa indica, Kofoid and Campbell, 1929, p. 217, fig. 397. 



The short lorica, with conical bowl, short, peglike aboral 

 horn, and numerous ribs, has a length of 2.15 oral diameters. 

 The oral rim is high, erect, ringlike, and sharp-edged. The 

 suboral trough is concave; the diameter of its outer margin 

 is 1. 17 oral diameters. There is a distinct suboral flare 

 (35°) within the upper o.i oral diameter. The bowl is 

 convex conical (15° in the anterior half, increasing to 45° in 

 the posterior section, and then 20°). The aboral end has a 

 prolonged, peglike horn with distal sharp point. 



The wall reaches 0.09 oral diameter in thickness suborally, 

 but thins rapidly in the middle. There are thin laminae 

 which enclose several layers of minute alveoles. There are 

 36 to 42 delicate, left-twisted (15°), sometimes branched 

 ribs, which die away on the swollen suboral flare. Fenestrae 

 are lacking. 



Length, 56 to 6311. 



Rhabdonella indica differs from R. amor in size, lack of 

 fenestrae, twist of the ribs, and more numerous ribs. It is 

 somewhat shorter than R. exilis, with fewer ribs and greater 

 density. It can scarcely be confused with other species. 



Recorded from twenty stations in the Pacific, as follows: 



three (36, 37, 39) in the Pacific equatorial region, four (46, 

 47, 78, 80) in the Galapagos region, three (48, 82, 90) in the 

 region of South Pacific island fields, one (58) in the South 

 Pacific middle latitudes, three (107, 109, 150) in the North 

 Pacific trade region, four (135, 136, 146, 147) in the Cali- 

 fornia region, and two (142, 145) in the North Pacific 

 middle latitudes. 



There are 24 pump and 6 net samples, of which 16 were 

 taken at the surface, 9 at 50 meters, and 5 at 100 meters. Max- 

 imum frequency, 6 per cent at station 46; other records above 

 minimum (2 to 5 per cent) from stations 48, 78; average in 

 net samples, 42 per cent; 2 to 15 loricae in pump samples. 



Temperature: pump samples i4?49-27?i2 (23727), net 

 samples i6?98-24?38 (22757). Salinity: pump samples 31.62- 

 36.44 (35.34), net samples 33.97-36.44 (35.50)- Density: 

 pump samples 20.20-26.07 (^S-SS)' "et samples 24.11-24.86 

 (24.45). pH: pump samples 7.85-8.32 (8.28), net samples 

 8.12-8.23 (8-I7). 



Rhabdonella inflata Kofoid and Campbell 

 Rhabdonella inflata Kofoid and Campbell, 1929, p. 217, fig. 403. 



The short, rather stout lorica, with chalice-shaped bowl 

 and wide aboral region, with little transition, has a length of 

 3.66 oral diameters. The oral rim is low, ringlike, and erect. 

 The suboral trough is flat and the diameter of its outer mar- 

 gin is 1.22 oral diameters. There is very little suboral flare. 

 The bowl tapers (5°) for nearly 0.4 total length and then 

 becomes subconical (33°) within 1.2 oral diameters. The 

 transition between lower bowl and horn is gradual. The 

 aboral horn has a length equal to that of the lower bowl, is 

 subconical (14°), and is sharply pointed at the free tip. 



The wall thickness reaches not over 0.06 oral diameter 

 suborally and thins down in the bowl. There are thin 

 laminae which enclose small alveoles in several layers. There 

 are upwards of 60 subvertical, mostly unbranched ribs, and 

 the intercostae have many small, faint fenestrae. 



Length, 124 to 20op. 



Rhabdonella inflata is shorter than R. spiralis, with grad- 

 ually differentiated horn and with more ribs. In similar 

 characters it differs from R. hebe, which last has a spindle- 

 like knob lacking in inflata. It is stouter than R. striata and 

 has fainter fenestrae. 



Recorded from two stations (131, 147) in the California 

 region, in net samples taken at 100 meters. Frequency, 2 

 per cent at station 131. 



Temperature, I2?i2-i9?27 (i5?69); salinity, 33.36-35.04 

 (34.20); density, 25.00-25.31 (25.15); pH, 8.29-8.32 (8.30). 



Rhabdonella lohmanni Kofoid and Campbell 



Rhabdonella lohmanni Kofoid and Campbell, 1929, p. 218, fig. 

 416. 



The tall lorica, with chalice-shaped bowl, oblique ribs, and 

 stout horn, has a length of 5.5 oral diameters. The oral rim 

 is low, ringlike, and slanted outward. There is almost no 

 suboral trough or suboral flare; the diameter of the bowl at 

 the upper end is, however, i.ii oral diameters. The upper 

 two-thirds of the bowl is subcylindrical, and the lower bowl 



