CONTRIBUTION TO THE PALEONTOLOGY OF TRINIDAD. 65 



It is also interesting as the first undoubted 36 species of Pholas ever described 

 from the Oligocene of either the Gulf States or the Antilles. 



Locality. — Along the shore 700 feet east of Brighton pier, Trinidad Island, in 

 an impure asphalt. 



Geological horizon. — Approximately equivalent to the Chipola (Upper Oligo- 

 cene) epoch of Florida. 



This species is named in honor of Mr. John Mack, of Philadelphia. 



Genus MARTESIA (Leach) Blainville, 1824. 

 Martesia oligocenica new species. Plate IX, Figures, 32, 33. 



Description. — Shell rather small, ovate-oblong, inequivalve; anterior end 

 short, roundly gaping, obliquely truncate; posterior end elongate, obtusely 

 pointed; smaller valve lying within the posterior margin of the larger; furrow 

 well marked, slightly oblique, placed near the anterior end of the valve; anterior 

 surface sculptured with fine, slightly imbricated lines of growth. 



Length of shell 14, height 8, diameter 7 mm. 



Remarks. — This is the first undoubted species of Martesia yet recorded from 

 the Oliogcene of the southern United States or the Antilles. 3 * 



It is evidently closely related to the recent and Pliocene species, Martesia 

 striata, Linn., of which it may be an ancestral form. M. striata has been found 

 in the Pliocene of Trinidad and Costa Rica. 



Locality.— Southern main road just south of Pitch Lake, Brighton, Trinidad, 

 in a yellowish-brown, ferruginous layer. 



Geological horizon. — Upper Oligocene. 



Class GASTROPODA. 



Genus CYLICHNA Loven, 1846. 

 Cylichna solivaga new species. Plate X, Figure 1. 



Description. — Shell small, rounded cylindrical; substance thin; spire invo- 

 lute, sunken; surface of shell entirely smooth and unsculptured except for fine 

 microscopic striae over the lower basal fourth of the shell; other characters con- 

 cealed by the matrix. 



Height of shell 9.5, greatest diameter about 5 mm. 



Remarks. — A single imperfect specimen of this species was found. 



It is more convex than C. sylvoerupis Harris from the Alabama Lignitic and 

 does not appear to be identical with any other species described from the lower 

 Eocene horizons. 



Locality.— Bed No. 8, Soldado Rock, Gulf of Paria. 

 Geological horizon. — Lignitic Eocene. 



* A shell from the Bowden beds of Jamaica was referred with a question by Dr. Guppy to this 

 fenus and described by him as Pholas t sphceroidalis. See also footnote 36. 



According to Dr. Dall Af. svhaeroidalift Cliinnv from .Tamnina is nrnhablv referable to another 



group 



JOURN. ACAD. NAT. SCI. PHILA 



