J BULLETIN 161, UNITED STATES NATIONAL MUSEUM 



Family LAGENIDAE 

 Subfamily Nodosariinae 



Genus ROBULUS Montfort, 1808 



Robulus Montfort, Conch. Syst., vol. 1, p. 215, 54th genre, 1808. 



Synonyms: Phonemus Montfort, 1808; Pharamuyn Montfort, 1808; Patrocles 

 Montfort, 1808; Spinderules Montfort, 1808; Herion Montfort, 1808; 

 Rhinocurus Montfort, 1808; Lam-pas Montfort, 1808; Scortimus Mont- 

 fort, 1808; Linthuris Montfort, 1808; Astacolus (?) Montfort, 1808; 

 Periples Montfort, 1808; Robulina d'Orbignt, 1826; Cristellaria (part) of 

 authors. 



Genoholotype. — Robulus cultratus Montfort. 



Test planispiral, bilaterally symmetrical, typically close coiled, 

 usually involute; chambers numerous, triangular in side view; wall 

 very finely perforate, glassy; aperture an elongate slit on the median 

 line of the usually somewhat concave apertural face in addition to 

 the radiate aperture of the outer peripheral angle. Jurassic to Recent. 



It is often difficult to distinguish between Robulus and Lenticulina. 

 In the Jurassic, where Robulus is the dominating genus, the distinc- 

 tions are much greater. In Recent material, however, the apertural 

 chamberlet has been developed with a radiate external aperture, and 

 in the species assigned to Robulus the median ventral opening is 

 usually more elongate and enlarged. It is, however, difficult in all the 

 genera of the Lagenidae to draw hard and fast lines between generic 

 characters. 



ROBULUS RENIFORMIS (d'Orbigny) 



Plate 1, F igures 2, 3 



Cristellaria reniformis d'Orbigny, Foram. Foss. Bass. Tert. Vienne, p. 88, pi. 3 

 figs. 39, 40, 1846. 



Test planispiral, very much compressed, often nearly twice as long 

 as broad, periphery acute but usually not strongly keeled; chambers 

 distinct, fairly numerous, 8 or 9 in the adult coil, early portion com- 

 pletely involute, later chambers becoming more elongate and slightly 

 evolute; sutures distinct, rather strongly curved, those of the last- 

 formed portion somewhat sigmoid, slightly limbate; wall smooth, 

 very finely perforate; aperture slightly produced, radiate, at the 

 peripheral angle of the test. Length, up to 1 mm; breadth, 0.45 mm; 

 thickness, 0.12 mm. 



Two specimens of this species are figured, one coming from Albatross 

 Station H3875, southwest point of Tahanae, about one-half mile off- 

 shore, 3 miles northeast, in 269 fathoms, and the other from Rangiroa. 

 These specimens are comparatively small, but seem to fit more nearly 

 d'Orbigny's description and figure of his species as described from the 

 Miocene of the Vienna Basin than some of the later figures that 

 have been referred to his species. 



