DESCRIPTION OF A NEW GENUS AND SPECIES OF INARTICULATE 

 BRACHIOPOD FROM THE TRENTON LIMESTONE.* 



BY 



Charles I). Walcott, 



Honorary Curator of the Depa r nverlebrate Fossils. 



Among the fossils collected by Mr. William P. Rust, in the vicinity 

 of Trenton Falls, New York, I discovered two specimens of a small con 

 ical shell closely related in form to Acrotreta subconica Kutorga.'t The 

 study of these in connection with one that I found at the same locality 

 in 1874 leads me to consider the shell to belong to a new genus and 

 species of the family Siphonotretidw. For it I propose the name Cono- 

 treta rusti. 



CONOTRETA gen. dot. 



In external form the conical or dorsal valve is similar to that of Acro- 

 treta gemma. The flat valve is unknown. In Acrotreta there is an 

 elongated muscular scar extending from each side of the siphonal tube 

 obliquely forward. In Conotreta five uarrow ridges radiate from the 

 apex towards the front, as shown in figures 1 and 2. The central ridge 

 joins the thickened apex, which, judging from the same characters in 

 Acrotreta gemma, was perforated by a siphonal tube. Structure cal- 

 careo corneous. 



Type, Conotreta rusti. 



Conotreta rusti sp. nov. 



Larger or dorsal valve more or less acutely conical, rounded — subtri- 

 angular at the margin of the valve : false area nearly flat, narrow and 

 grooved at the center by a longitudinal, narrow, shallow furrow; prob- 

 ably perforate at the apex. Surface marked by concentric lines of 

 growth that pass uninterruptedly over the false area. 



The cast of the interior of the conical valve shows six narrow, elon- 

 gate ridges radiating from the apex, that separate five depressions on 



*Read before the Biological Society of Washington, November 30, 18i-9. Advance 

 sheets of this paper were distributed December 10, 1-~ ( J. 



fUeber die Brachiopoden-Familie der Siphonotretsese, p. 28, p). ?, 6g. 7. Veruandl. 

 Kaiserl. Min. Geeellschaft, St. Petersburg, 1-!-. 



Proceedings National Musi urn. Vol. XII — No. 775. 



3C5 



