AMERICAN LOCALITIES OF TETR AG R AM JI A . 



liamson,^ and numerous specimens of an Eulosolenia, resembling the E. r/hhnm of 

 Williamson, which is abundant in a fossil state in the Miocene tertiary of Vir- 

 ginia, and which appears to be a cosmopolite in the present seas, as I have found 

 it not only in American soundings, from Massachusetts to the Gulf of Mexico, but 

 also in muds from the Island of St. Helena, and from Bombay. 



No locality on our northern coast has furnished such an abundance of Polytha- 

 lamian forms as the one at Edgartown; and it is worthy of inquiry whether oceanic 

 currents, or some peculiarity of the neighboring rocks, can have affected the fauna 

 of this place. 



V. 



American Localities of Tetragramma. 



In the Berl'm MonatsbericU for May, 1843, Ehrenberg gives the following cha- 

 racters for the genus Tetrafjramma : — 



" Genus e familia Bacillariorum, sectione Naviculaceorum. Lorica, simplex 

 bivalvis silicea, compressa quadrata libera latior quam longa unilocularis, septis in 

 medio loculo binis medio interruptis ibique dihitis in forman 4 signorum musico- 



rum." 



He states also that the only species known to him is nearest allied to the Te7-2> 



sinoe musica. 



The specific characters of the Asiatic species, T. As!a(ica,Ehr., are not given, nor 

 have I seen any drawing or specimens of it. The generic characters, however, as 

 above given, agree so well with an American form, that I have no doubt that we 

 have a species of the genus occurring in considerable abundance upon the North 

 American coast of the Atlantic. 



As the Asiatic species is unknown to me, I shall, for the present, keep our spe- 

 cies distinct from it, and propose for it the name Tetrarjramma americana, and the 

 following specific characters : — 



TetragraiiHiia americana, B. 



Lorica quadrangular, resembling that of Terjosinoe musica, Ehr., but smaller, 

 more minutely punctate, and showing on 

 each side only two of the internal bodies, 

 resembling notes of music. The end view 

 shows an undulating outline (see Fig. 1, 

 A b), with two cross-bars, which separate 

 the inflated central portion from the nar- 

 rower three-lobed ends. By comparing the 

 outline (Fig. 1, A, b) of T. americana with 

 the accompanying ones (Fig. 2, C d), of 

 Terpsinoe musica, their chief points of re- 

 semblance and disagreement wall be seen. 



Fig. 1. 



Il 





■N 



, 





■ 



V 







' See Annals and Magazine of Natural History, 2cl series (Plate I. Fig. 1), for January, 1848. 



