ORTHAULAX, A TERTIARY GUIDE FOSSIL. 



29 



concealing the whorls of the spire, and duplicating fur a 

 very considerable extent the outer lip; spire freely in- 

 closed in a pointed superstructure, or dome, liuilt over it 

 by an extension of the mantle; surface covered with lon- 

 gitudinal lines of growth, which extend continuously 

 from the apex to the base. 



Length (of imperfect specimens, lacking probal)ly 

 upward of an inch), 2.7 inches; width, 1.75 inches. 



What the precise relationship of the genus represented 

 by this species may lie I am not prepared to say. 



Zittel (Handbuch der Palaeontologie, I, part ii, p. 260) 

 unites Orlhaulax with Hippochrenes, liut in doing so this 

 eminent paleontologist appears to have been misled liy 

 the rather imperfect diagnosis of the fossil given by Gabb. 

 That its position is near to that genus I believe there can 

 be no doubt. 



As has been pointed out by Dall (see p. 27), 

 Heilprin mistook a solution cavity in his speci- 

 men for a natural feature of the shell. Such a 

 hollow dome would indeed be remarkable. 



Orthaulax piKjrM.r is so like Orthanlax gahbi 

 that it seems surprising that the resemblances 

 between them were not pointed out long ago. 

 Young sbclls of both species are almost circu- 

 lar in outline, but older shells are strongly 

 triangular. The outlines of the anterior part 

 of the whorl as shown in figures of the type of 

 0. pugnax can be matched perfectly by speci- 

 mens of 0. gahbi, but other specimens of 0. 

 pugnat appear to have proportionately longer 

 and less top-shaped whorls than 0. .gahbi. 

 The most conspicuous difference between the 

 two species consists in the shape of the posterior 

 end of the adult shell, which in 0. gahbi is 

 nearly always more or less rugose but in 0. 

 pugnax appears to be usually smooth. How- 

 ever, the range in variation in 0. gahbi is so 

 great that many specimens are as smooth as 

 0. pugnax. 



Because of the scarcity of authentic speci- 

 mens of (>. pugnax and the unfavorable state 

 of their preservation, no axial sections of speci- 

 mens from the type area have been cut, and it 

 is not likely that attempts to cut the available 

 material would yield satisfactory results. How- 

 ever^ a small specimen from Antigua (PI. II, 

 figs. 3a, 3b), which seems to be <). pugnax, 

 shows that the layers of callus are almost 

 evenly lunate, as in (). caepa, but thicker than 

 in 0. caepa and not knobby, as in most speci- 

 mens of 0. gahbi. Another small specimen 

 from the Canal Zone which I had previously 

 identified as O. pugnax '' shows a tendency to 

 knobbiness in the callus and also possesses a 



II U. S. Nat Mus. Bull. 103, pp. 550, 553, 1919. 



much more rapidly tapering living chamber 

 like that in some specimeiis of 0. gabhi. I 

 have therefore referred it to 0. gabhi. 



LocaHties: Ballast Point, Tampa Bay, Fla., 

 U. S. Nat. Mus. catalogue Nos. 11207.5, Burns, 

 collector, 165100, E.J. Post, collector; Bailey's 

 Mill Creek Sink, thi-ee-fourths mile northeast 

 of Lloyds, Jefferson County, Fla., from clay 

 overlying a limestone, L. C. Johnson, collector, 

 U.S. Nat. Mus. catalogue No. 112521; Hales 

 Landing, Flint River, Ga., 7 miles below Bain- 

 bridge, Vaughan, collector, 1900, station 3383, 

 U.S. Nat. Mus. catalogue No. 166787 (labeled 

 O. inornaius) ; Hales Landing, Flint River, Ga., 

 Vaughan, Cooke, and Mansfield, collectors, 

 1914, station 7074, U.S. Nat. Mus. catalogue No. 

 166788; Blue Springs, Flint River, Ga., Pum- 

 pelly, collector, U. S. Nat. Mus. catalogue No. 

 115747; H miles southwest of Geneva, ^Vla., 

 Clapp, collector, station 8867 ; Antigua, Spencer, 

 collector, U.S.Nat. Mus. catalogue No. 166984. 



Orthaulax gabbi Dall. 



Plate III, figures 5-7; Plate IV. figure 1. 



Orlhaulax gabbi Dall, Wagner Free Inst. Sci. Trans., vol. 



3, p. 170, pl. 12, figs. 5, 5a. 5b, 1890; U. S. Nat. Mus. 



Bull. 90, p. 87, 1915. 

 Orlhaulax innrnaluji Dall (part), U. S. Nat. Mus. Pnic, p. 



.509, 1916. 



Orthaulax gabbi has been well described by 

 Dall as follows (1890): 



Shell large, solid, many-whorled; in the very young 

 smooth and polished, except for incremental lines and a 

 few faintly impressed spiral lines anteriorly; nucleus 

 small, polished, glassy, not differentiated from the rest 

 of the shell; early whorls with a very distinct, not chan- 

 neled suture; the whorl in front of it slightly turreted; each 

 whorl after the third has three slightly elevated, narrow, 

 rounded varices, somewhat irregularly spaced, so that 

 they do not follow each other continuously down the slope 

 of the spire; aliout the end of the eighth whorl the poste- 

 rior edge of the outside whorl liegins to lie prolonged liack- 

 ward moro and more as the shell grows, so that the suture 

 thus formed makes an irregular spiral line ascending the 

 spire over the antecedent whorls until by about the tenth 

 turn the whole of the spire is enveloped, as well as any 

 l)arnacles, vermetus, or other semiparasitic growth which 

 may have liecome attached to the surface of the spire; the 

 anterior part of the shell has the shape of Lnorhynus; the 

 pillar is rather thick and slightly recurved, with a moder- 

 ately distini't fasciole: the canal moderately wide, shorter 

 than tlie jiillar; the outer lip simple, sharp, a little thick- 

 ened at the resting stages, but not lirate internally: l)ody 

 with a moderate callus, which at the resting stages is con- 

 sideraljly enlarged, so that when the whorl comes to grow 

 over it (as it is not absorbed) it produces an irregularity 



