TAXONOMY AND DISTRIBUTION 



55 



level at which the cone widens it is 1.04. At the aboral end 

 is a narrower (23 ), scarcely prolonged point which is the 

 homologue of the aboral horn of other species. There are 

 6 narrow (0.02 oral diameter), equidistant, decurrent blade- 

 like ribs which extend from the aboral end to the lower edge 

 of the collar. These ribs do not branch and are strictly 

 vertical. 



The wall is hyaline and without fenestrae, and is thickest 

 just below the collar, where it reaches twice the width of the 

 cuff that rests on it; it gradually thins and is only three-tenths 

 as thick in the lower bowl. There are thin laminae, but 

 prisms were not evident between them. 



Length, =52 to 98^1. 



There is considerable variation in length and proportions, 

 probably correlated significantly with temperature. The 

 number of ribs (6 to 10) is interesting. 



Protorhabdonella simplex resembles P. curta, but its ribs 

 are considerably fewer, and vertical. The bowl is longer and 

 narrows less quickly. It resembles P. ventricosa in having 

 few ribs, but that species is widely expanded toward the 

 aboral three-tenths (almost 1.4 oral diameters). It is unlike 

 Rhabdonella amor, in which the ribs are lower, twisted, 

 branched, and numerous, and which has a higher collar. 



Recorded from eighteen stations, four in the Atlantic and 

 fourteen in the Pacific, as follows: two (20-21, 21) in the 

 Sargasso Sea, two (23, 24) in the Atlantic equatorial region, 

 six (41, 4=;, 46, 69, 77, 78) in the Galapagos region, four 

 (61, 63, 64, 66) in the South Pacific middle latitudes, two 

 (102, 109) in the North Pacific trade region, one (131) in 

 the California region, and one (143) in the North Pacific 

 middle latitudes. 



There are 9 pump and 18 net samples, of which 10 were 

 taken at the surface, 7 at 50 meters, and 10 at 100 meters. 

 Maximum frequency, 8 per cent at station 61; other records 

 above minimum (2 to 5 per cent) from stations 21, 41, 45, 

 46, 69, 77, 78; averages in net samples, 1.3 and 3.1 per cent 

 for the Atlantic and Pacific, respectively; average in pump 

 samples, 1.5 loricae. 



Temperature: Atlantic, net samples i5?55~26?57 (2i?88); 

 Pacific, pump samples i4?55~25?73 (20?72), net samples 

 i2?i2-23?72 (20?65). Salinity: Atlantic, net samples 35.61- 

 36.28 (36.03); Pacific, pump samples 34.39-36.17 (35.14), 

 net samples 33.36-36.04 (34.89). Density: Atlantic, net 

 samples 23.84-26.34 (24.98); Pacific, pump samples 23.65- 

 26.11 (24.63), net samples 24.06-25.31 (24.52). pH: At- 

 lantic, net samples 7.96-8.32 (8.17); Pacific, pump samples 

 7.92-8.30 (8.24), net samples 8.05-8.32 (8.15). 



Protorhabdonella striatura Kofoid and Campbell 

 Protorhabdonella striatura Kofoid and Campbell, 1929, p. 20K, 



fig- 392- 

 The elongated, conical, chalice-shaped lorica, with numer- 

 ous ribs and narrow conical aboral horn, has a length of 

 4.88 oral diameters. The oral margin is thin and erect. The 

 collar is a basal segment of a cone (21 °) and has a length of 

 about 0.5 oral diameter; its diameter at the lower end is 

 0.91 oral diameter. The elongated bowl gradually expands 



from the throat to nearly 1.2 oral diameters near 1.65 oral 

 diameters below the rim. Below ibis level the bowl steadily 

 contracts (22 ) within less than 2.2 oral diameters, forming 

 an inverted segment of a cone. The pedicel is an inverted 

 asymmetrical cone (18 ) with a length of 1.46 oral diameters. 



The rather transparent wall has 24 vertical ribs, a few of 

 which branch in the upper three-tenths of the bowl. There 

 are a few (6 to 8) small circular fenestrae scattered in a zone 

 within the posterior part of the bowl above the pedicel. The 

 wall is thin (about 0.02 oral diameter), with slight thicken- 

 ing at the throat. 



Length, 125 to 165(1. 



Protorhabdonella striatura differs from P. mira in having 

 a shorter pedicel and more ribs, and in contraction at the 

 throat. The other species of the genus have weaker devel- 

 opment of the pedicel. 



Recorded from one station (27) in the Atlantic equatorial 

 region, in a pump sample taken at 50 meters. Frequency, 

 2 loricae. 



Temperature, 26?04; salinity, 56.25; density, 23.98; pH, 

 8.30. 



RHABDONELLA Brandt emended 

 Rhabdonclla, Kofoid and Campbell, 1929, pp. 209-211. 



Rhabdonella is related to the much smaller, simpler Proto- 

 rhabdonella, and to the more complex Rhabdonellopsis. The 

 dominant structure in this genus is the vertical ribs. These 

 suggest the possible origin of the genus in some member of 

 the Favellidae or the Ptychocylidae, in which there are 

 many short surface pleats, and also suggest relationship to 

 the more advanced genera of the Epiplocylidae. 



Rhabdonella occurs in tropical seas, there being little or 

 no limitation of species to any of the oceans save, perhaps, in 

 a few rare and little understood species, such as Rhabdonella 

 aberrans. 



Eighteen species are described here. 



Rhabdonella amor (Clcvc) Brandt 

 (Figure 85) 



Rhabdonella amor, Kofoid and Campbell, 1929, p. 212, fig. 398; 

 Marshall, 1934, pp. 649-650, fig. i<>. 



The small lorica has a high suboral rim, conical bowl, and 

 pointed aboral end; its length is 1.9 oral diameters. The oral 

 rim is ringlike, sharp, and high. The suboral trough is deep 

 and concave, and the diameter of its outer margin is 1.15 oral 

 diameters. There is little suboral flare. The bowl is dis- 

 tinctly conical (14 in the upper two-fifths, then 46°, and 

 finally 40 in the lowermost fifth). The aboral end is 

 pointed, sharp, and not prolonged. 



The wall has a thickness of 0.1 oral diameter suborally, 

 and progressively thins in the bowl. There are thin laminae 

 which enclose several layers of exceedingly minute alveoles. 

 There are 32 to 44 left-deflected (as much as 12 ), commonly 

 branched and anastomosed ribs. The intercostae have 15 to 

 20 single or double rows of large oval fenestrae which pass 

 across the laminae and enclosed alveoles. 

 Length, 77 to 98a. 



Marshall's 2 figured loricae are unusual in shape and in 



