CONTRIBUTION TO THE PALEONTOLOGY OF TRINIDAD. 83 



Trinidad shell has two rows of tubercles on the last volution. No doubt the 

 Trinidad shell is the ancestral form of the living C. tectum. 



The history of the description of the fossil shell is interesting. In 1873 Gabb 

 found in the " Miocene " of Santo Domingo a large series of shells, similar to the 

 specimens from Trinidad now under discussion, which showed a remarkable 

 tendency to variations. He referred them to Cuma tectum Wood and remarked : 56 

 "This well known Panama shell is very common in the Santo Domingo beds, and 

 goes through an astonishing series of variations. I have it with a rounded body, 

 without a tubercle, and varying from that to a broadly angulated and umbilicated 

 form, with six immense tubercles on the angle. Between these, and other ex- 

 tremes, I fortunately possess complete series connecting them without question/' 



But in I860 57 Gabb had described Fasciolaria woodii from the " Miocene' ' 

 marl near Shiloh, New Jersey. This is a nearly smooth form, externally not 

 unlike a young Fasciolaria. Indeed, with only the two extremes to compare, 

 one could not believe that the nearly smooth New Jersey form and the strongly 

 tuberculated southern form are the same species. However, Dr. Dall on examin- 

 ing the type shell of Gabb's Fasciolaria woodii from New Jersey found that it was 

 a typical Cymia. Later, on studying Gabb's series of "Cuma tectum" from 

 Santo Domingo, he found that the smooth varieties grade perfectly into the 

 New Jersey form. Hence the species called by Gabb Fasciolaria woodii and 

 those referred by him to "Cuma tectum" from Santo Domingo are identical 

 specifically. In Dr. Dall's opinion, however, the "Cuma tectum" of Gabb 

 from the Santo Domingo beds is not the same species as the Cuma tectum of 

 Wood and of Kiener, a recent species common in the Panama region and found 

 along the west coast of Central America as far south as Ecuador (Newcomb). 

 Dr. Dall says: 58 "On examining the unique type of Gabb's Fasciolaria woodii 

 I saw at once that it is a typical Cymia; but my astonishment was great when, 

 on looking over the large series of the Miocene fossil from Santo Domingo 

 which Gabb had referred to Cuma tectum, I found that the two could not be 

 separated specifically, and that neither should be referred to C. tectum. 



"The C. woodii is a very variable shell with or without tubercles and periph- 

 eral carina, and varying much as some Purpuras do. The fine series at Phila- 

 delphia shows this well, and among the smoother varieties the exact duplicate of 

 the New Jersey fossil can easily be found." 



Dr. Dall 59 calls attention to the fact that Conrad's Tritonopsis subalveatum™ 

 may be this species, as it is a true Cymia. It was found at the base of the Vicks- 

 burg beds (Lower Oligocene) of Mississippi, but no positive specific identifica- 

 tion of it has been made. 



56 Trans. Am. Phil. Soc, XV, p. 214, 1873. 



57 Jour. Acad. Nat. Sci. Phila., 2d ser., IV, p. 375, pi. 67, fig. 7, 1860. 



58 Trans. Wagner Inst, of Sci., Ill, p. 155. 

 69 Trans. Wagner Inst. Sci., vol. Ill, p. 155. 



60 Jour. Acad. Nat. Sci. Phila., 2nd ser., II, p. 41, pi. 1, figs. 2, 8, 1850= Triton subalveatum, op. cit., 

 I, p. 207, 1849. 



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