Appendages of Triarthrus Beckii. 123 



Within the past few months Mr. "W. S. Valiant has collected 

 a very considerable number of specimens of Triarthrus Beckii, 

 in which the organs of the under side are attached to the body 

 and fairly well preserved. They occur in the Hudson River 

 shales* near Rome, !N\ Y. A number of the best specimens 

 are now in the Museum of Columbia College, and Prof. 

 Kemp has very kindly given me the privilege of describing 

 them. 



The trilobites are found in a soft, fine, black shale and are 

 very perfectly preserved. The most noticeable character about 

 them is the presence of long, many jointed, rod-like attach- 

 ments to the front of the head, which resemble exactly the 

 antennae of other crustaceans. These come out close together 

 from just under the center of the anterior border of the head- 

 shield, and diverge generally at an angle of 30° or 40°. In 

 one specimen (fig. 1) a length considerably exceeding that of 

 the glabella is shown ;f in the rest they are more broken, but 

 a considerable length is preserved in three or four, and the 

 stumps are distinctly seen in upwards of twenty others. They 

 curve slightly outward and taper gradually down toward the 

 end ; the tip itself is not preserved. These antennae are com- 

 posed of a great number of joints, each of which is conical, 

 about half as long as wide, and smallest at the base. (See fig. 

 la.) As preserved in the rock, they are calcareous, but seem 

 to have been of a structure less firm and thick than the sub- 

 stance of the carapace. Their point of origin seems to be 

 under the front part of the glabella, as they can be traced a 

 little way under the headshield, where they almost coalesce, 

 then turn upward and outward and disappear ; with no joints 

 in this part, so far as I have been able to follow it. (See fig. 

 2.) Just over the spot where they come out, the anterior mar- 

 gin is arched slightly upward, seemingly to give room for 

 their play to and fro. 



These organs must certainly belong to the trilobite ; when 

 attached they are in all cases in exactly the same position, and 

 are but rarely to be seen separate ; moreover, in a number of 

 specimens in which they were not shown they were developed 

 by cutting away the matrix in the proper place. Their char- 

 acter seems also tolerably certain, as both in position and struc- 

 ture they are like the antennae of modern crustaceans. The 

 appearance of the right hand antenna in fig. 3 may indicate 

 that these organs could be bent back under the sides of the 

 head — but this point needs more evidence. Another specimen, 



* Though referred to the Hudson River hy Mr. Valiant, Prof. Whitfield is dis- 

 posed, on paleeontological grounds, to consider them as Utica shales. 



f Mr. Valiant has since shown me a specimen which has antennas one and a 

 half times as long as the glabella. He informs me that there are now about sixty 

 specimens showing antennte. 



