30 



SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1921. 



somewliat like a varix: the whorla arc ovately rounded, 

 smooth, except for oecasional transverse undulations due 

 to irregularities of growth, and polished; no indications of 

 color pattern have been observed. 



The adolescent form a good deal resembles a Stroinbiis 

 except that the anterior sulcus of the outer Hp behind the 

 canal is absent or represented only by the faintest wave 

 in the margin; (he spire is entirely enveloped liy the 

 ba<-k\vard prolongation of the last whorl, except at the tip. 

 where the envelojje is usually a little eroded or defective; 

 there appears to be a resting stage at every two-thirds of a 

 revolution of the whorl around the axis, for which reason, 

 looking down on the spire, the outline of the shell trans- 

 verso to the axis is subtriangular or three-sided; the outer 

 lip is simple, rather sharp-edged, and very slightly, if at 

 all. recurved; it extends liackward to the tip of the spire, 

 near which it recedes somewhat from its parallelism with 

 the axis; at the shoulder, also, it is slightly excavated and 

 thii'lvened: the body is smooth, with a moderate callus, 

 which liecomes thicker near the shoulder; at the shoulder, 

 in front of the excavation above noted, it becomes very 

 thick and is continued on to the spire parallel with the 

 outer lip, and very near it, so that between the two is a 

 narrow, flexuous groove of considerable depth; when the 

 shell l)egins to .gi'ow again the whorl is carried over this 

 ridge, wliich is not absorbed, and the surface is thus ren- 

 dered, as it were, varicose; the canal is short, strongly 

 recurved, with a remarkably deep sijjhonal sulcus, so 

 that the end of the pillar stands forward in a marked way; 

 on the shoulder, halfway around the shell, is an ill-defined 

 naiTow ridge, whidi ceases a little way behind the lip. 

 The dimensions of tlie figured specimen are: Longitude, 

 fi.S millimeters; maximum latitude, 35 millimeters. 



The adult form differs from the adolescent by the dis- 

 proportionate strength of the ridge at the shoulder, by 

 whirli the surface liehind the ridge has become flattish, 

 as in a (Cassis, but more irregular, and the width at the 

 shoulder has increased in proportion to the total length. 

 No entirely complete specimen of the adult has been found, 

 but from numerous fragments the proportions can be ap- 

 proximately determined. The maximum diameter is 

 71 millimeters, and the length about 11 millimeters, of 

 which 15 millimeters are behind the shoulder, wliile, in 

 the specimen only fiS millimeters long, there are 17 milli- 

 meters of length beliind the shouliler. 



This species appears abundantly, though in a poor state 

 of preservation, in the lower bed at Alum Bluff and in the 

 ("hipola beds to the westward. The group in America 

 would seem to be characteristic of the lower lieds of the 

 southern Miocene, as far as our present knowledge per- 

 mits VIS to judge. 



1 have observed that, occasionally, the ridge on the 

 slioulder in young s|X'cimens is re]iresented liy a nodule 

 rather than a ridge. 



The resemblance of 0. gahbi to 0. piujnax is 

 noticed under the description of Orthaulai 

 jmgiiax. 



Localities: Tenmile Creek, 1 mile west of 

 Bailey's Ferry, Cliipola River, Fla., Burns, 

 collector, station 2212; 1 mile below Bailey's 



Ferry, banks of river above white limestone 

 bed. Burns, collector, 18S9, station 2213; 

 right bank of Chipola River on McCleland 

 farm, 1 mile below bridge at old Bailey Ferry, 

 Calhoun County, Fla., Dall, collector, 1893, 

 station 2564; same locality, Vaughan, col- 

 lector, 1900, station 3419; lower bed at Alum 

 Bluff, Apalachicola River, Fla., Burns, col- 

 lector, 1889, station 2211; same locality, Cooke 

 and Mansfield, collectors, 1914, station 7183; 

 Panama Railroad, 2 miles south of Monte 

 Lirio, formerly known as Mitchellville, Canal 

 Zone, MacDonald, collector, 1911, station 

 5901; upper part of Culebra beds on west side 

 of Panama Canal about one-third mile north 

 of Paraiso, MacDonald, collector, 1913, sta- 

 tion 6515; topmost limestone in Gaillard 

 Cut opposite Las Cascadas, Canal Zone, Mac- 

 Donald and Vaughan, collectors, 1911, station 

 G019-g (two casts of the interior, identification 

 very doubtful). 



Type: U. S. Nat. Mus. 112218. 



Orthaulax aguadillensis Maury. 



Plate IV, figiu-es 2-0; Plate V, ligiues la, lb. 



Orthaulax aguadilloisis Maury, Scientific sm'vey of Porto 

 Rico and the Virgin Islands, vol. 3, pt. 1, p. 5.1, pi. 

 ;i, fig. 4, New York Acad. Sci., 1920. 



Ori/idulax pur/nax Cooke, C. W. (part), Carnegie Inst. 

 Washington Pub. 291, p. 115, pi. 2, fig. 15, 1919. 



Maury's description is as follows : 



Shell large and heavy; form of spii-e short and blunt, 

 like that of Orrhaidax pugnax. This at once distinguishes 

 the shell from the Dominican species 0. inornatus Gabb, 

 which is high-spired. A further characteristic of the shell 

 is the evenly rounded form of the shoulder, which in cross 

 .section would be almost perfectly circular. This marks 

 it oft very decisively from the Floridian Chipolan species 

 Orihaulax (jabhi Dall, which is markedly triangular at the 

 shoulder. The spire measures 45 millimeters in diameter. 



A single specimen of this Orlhauhix was collected by 

 Reeds at Aguadilla. It is imperfect but undoubtedly a 

 typical member of this very important index genus. 



The shell was submitted to Dall, who compared it 'with 

 the types of the various known species in the National 

 Museum. He replied that "The Orthaulax is nearest to 

 0. pugnax, but as the margin of the spire is gone it is 

 impossible to be certain. 1 think it is new." 



One might be criticize<l for describing so incomplete a 

 specimen as new were this a less rare and less stratigraph- 

 ically important genus. Moreover, no complete adult shell 

 of either 0. inornatus or 0. pugnax has ever been found. 

 Though heavy and apparently strong, the shells seem to 

 go to pieces very easily, and usually one finds only heads, 

 as in this case, or fragments of the heavy pillars. 



