12 SYRIAN MOLLUSCAN FOSSILS. 



Localities. — On the authority of Dr. Merrill, two specimens are from the 

 " Gilead Mountains," east of the Jordan, and from his collection. The third, 

 of which the dimensions are given above, is from Abeih or its vicinity, and 

 from the Bird Collection. 



Siraiigraphical Position. — Fraas regards the marl, of which this species is 

 the characteristic fossil, as marking the close of the Brown Chalk of German 

 systematists, and as introducing the superimposed Gray Chalk. This marl 

 and beds of some 170 meters in thickness which lie next above, he terms 

 the Zone of the Ammonites Syriacus, in his view the third member (ascending) 

 of the Turonian subdivision of the Cretaceous, as developed in Syria. Ac- 

 cording to the same authority, three zones more follow above before the 

 close of the Turonian and the commencement of the Senonian marl, cor- 

 responding to the White Chalk. We may then consider this species as 

 belonging to the middle portion of the Turonian of d'Orbigny, though 

 that author himself (Prodrome, II, Stage vingtieme, 11) referred it to his 

 Cenomanian (Upper Greensand), which next precedes his Turonian. 



Ammonites Vibrayeanus D'Orbigny. 



I, ... nites Vibrayeanus D'Orbigny, 1840, Paleont. Prang., Terr. Get., I, p. 322, PI. xcvi, figs. 1-3. 



Eight specimens, interior casts. In the compressed and flattened form, 

 thin, but truncate back, sagittate aperture, and general proportions, they 

 correspond so closely to d'Orbigny's description and figures of the species 

 above named, that I cannot hesitate to refer them to it. The best preserved 

 of the eight fully accords with d'Orbigny's description in having straight 

 ribs radiating from the umbilicus to the periphery. Yet it is to be noted 

 that the septal lobes agree better with those of .1. Syriacus than with the 

 lobes of A. Vibrayeanus, as figured by d'Orbigny. 



It must be of similar, but probably more imperfect specimens, that Fraas 

 remarks (Aus dem Orient. II. p. 78): "'The choice becomes difficult whether 

 we ought to reckon them witli Syriacus or with Vibrayeanus." 



Diameter of largest, 77 mm. The specimen mentioned above as tlie best 

 preserved has the dimensions: greatest .diameter, 68 mm.; greatest thickness, 



l'Jinm.; width of outer volution at the aperture. :17 mm. Coll. Thomson. 

 Locality and Position. — Probably the Beirut district; from same horizon 



as the last species. 



