ORTHAULAX, A TEBTIAKY GUIDE FOSSIL. 



27 



SYSTEMATIC PALEONTOLOGY. 



FamUy STBOMBIDAE. 

 Genus ORTHAULAX Gabb. 



Orthaulax Gabb, Acad. Nat. Sci. Philadelphia Proc, vol. 



24, p. 272, 1872. Type 0. iiiornatii.<i Gabb, op. cit., 



pi. 9, figs. 3, 4. Miocene of Santo Domingo. 

 Orthaulax Gabb, Am. Philos. Soc. Trans., new ser., vol. 



15, p. 234, 1873. 

 Hippochrenes (part) Zittel, Traits de pal6ontologie, vol. 



2, p. 258, 1887. 

 Wagneria HeUprin, Wagner Free Inst. Sci. Trans., vol. 1, 



p. 105, 1887. Type W. pugnax Heilprin, op. cit., 

 • p. 106, pi. IS, figs. 36, 36a. Oligocene of Florida. 

 Orthaulax Dall, Wagner Free Inst. Sci. Trans., vol. 3, p. 



169, 1890. 

 Orthaulax Dall, U. S. Nat. Mus. Bull. 90, p. 86, 1915. 



The following description of Orthavlax, 

 which is quoted from Gabb, 1873, difi'ers from' 

 the original description of the preceding year 

 only in a few unimportant verbal changes and 

 alterations ui punctuation which do not affect 

 the meaning : 



Shell rounded-fusiform, canal moderate, straight and 

 regularly tapering; adult shell enveloped over the whole 

 spire by the extension of the inner lip; posterior canal 

 fissure-like, formed l)y the continued edge of the outer 

 lip and running directly to the apex. Outer lip apparently 

 sharp and simple; anterior notch oblique and liroad. 



The discovery of this genus fills an important break in 

 the Rostellarias, uniting the true genus Rostcllaria with 

 Conrad's Calyptraphorus. Unlike both of these genera 

 the canal is not styliform l)ut robust and comparatively 

 short, and its terminal not<:h is formed l)y an almost rec- 

 tangular truncation of the anterior portion of the outer 

 lip. Like Bostfllarw, it has a straight posterior canal, 

 prolonged, however, further than is common in that 

 genus. The canal is similar in structure to that of Calyp- 

 traphoru^, being formed by a squamosa plate; but in the 

 latter genus it curves over backwards, liehind the spire, 

 which it ascends to about half its height and then bends 

 down to near the suture of the body whorl. Unlike the first 

 and like the second of its congeners, it has the whole 

 spire enveloped in a plate which should more properly 

 be described as a posterior extension of the body whorl, 

 carrying the suture to the extreme apex. The lines of 

 growth run from the top of the spire to the anterior end of 

 the shell. It carries none of the tubercles seen in Calyp- 

 traphorus and Tessarolax and seems, unlike most of the 

 other genera of the family, to have had a simple outer 

 Up, neither digitate nor notched. 



The following excellent description of Or- 

 thaulax is taken from Ball's Tertiary fauna 

 of Florida: " 



This group was described liy GabI) from immature 

 specimens, and no perfect specimen has hitherto been 

 figured, for which reason a good deal of doubt has rested 

 upon it. 



!i Wagner Free Inst. Sci. Trans., vol. :i, pp. 169-170, 1S9U. 



At first, when 1 examined young specimens of a genuine 

 Orthaulax I was struck by their resemblance to Leio- 

 rhynus Gabb, and at once suspected that the latter was 

 only a young specimen of the former. But on examining 

 the type species of Lciorhynus I found that tliis was not 

 the case, since that shell liore evidences of maturity, has a 

 thickened and Urate li]i, is not self-enveloped by the last 

 whorl, and has numerous varices. It is, in short, a form 

 which ])erraanently retains some of the external features 

 of immature Orthaulax wiiile adding to them others which 

 are not found in Orthaulax. 



The genus Wa/pirria of Heilprin is founded on charac- 

 ters which are simply part of the process of mineraliza- 

 tion. The type of Wagntria is a siliceous pseudomorph; 

 the \'ery thick coating of the spire ha\'ing lieen only par- 

 tially replaced by sUica, thus lea-ving a hollow, geodic 

 dome analogous to nothing in the original shell. 



.\ similar state of affairs is found in many of the fossUs 

 of that locality, \vhich present a thickness too great to 

 permit of soUd silicification. All the corals, some of the 

 Turritellas, etc., offer examples of this kind. For the 

 rest, the relation of his shell to Orthaulax was not over- 

 looked by Prof. Heilprin, though he was misled by the 

 state of his material. The name Wagneria in any event 

 was preoccupied, and if the genus had proved vaUd another 

 name would ha\'e had to be substituted. 



Orthaulax is almost intermediate lietween Rostrllaria 

 and Stroiiihus. It differs from Hippochrenes Montfort, to 

 which it was referred l)y Guppy and Zittel, in the following 

 characters: 



It has not the long, anteriorly produced pillar, nor the 

 widely expanded outer lip; Hippochrenes has the last 

 whorl, when adult, posteriorly extended to the tip of the 

 spire, marking the conclusion of its growth; Orthaulax 

 while very joung has the whorls gradually ascending 

 upon the normal ju\enile spire by such an expansion, 

 which, when developed, is continuous, enveloping the 

 whole spire, coiling round and round it as the whorls 

 grow, and completely concealing the whole of the spire, 

 nothing but the outside of the last whorl being visible in 

 an adult specimen. 



The following additional remarks on the 

 genus are added by Dall in the same volume, 

 page 172, after his description of the species 

 0. gabhi: 



The essential difference between Orthaulax and Hip- 

 pochrenes, Calyplrophorus. Riniella, etc., is that the invo-' 

 lution of the spire, once commenced, is carried on by the 

 posterior edge of the last or growing whorl continuously 

 from the young condition in Orthaulax; while in the others 

 the spire remains normal until the shell reaches its adult 

 state and then, with the changes in the mantle, which 

 incite the deposition of the thickened and enlarged outer 

 lip, a process is developed at the posterior commissure of 

 the aperture and mantle, which deposits enamel on the 

 spire against which it lies, and it thus forms a gutter, some- 

 times straight, sometimes recurved, in which it is shel- 

 tered; apart from this the spij'e is enveloped, if at all, not 

 by any expansion of the lip, but by a deposit of enamel 

 which covers the whole, as frosting does a cake, without 

 any relation to the coil of the shell considered as an organic 

 product. Strip off the whole envolving, continuous 



