i894. NOTES AND COMMENTS. 329 



necessary to allow for the deposition of the strata of any given zone a 

 vastly greater length of time than has hitherto been conceded, or 

 whether Dr. Walther's explanation, quoted in our last number 

 (p. 245), will suffice — these are questions that will soon demand an 

 answer. 



The Legs of Trilobites. 



In Natural Science for September, 1893, we called attention 

 to the interesting discoveries of Messrs. Valiant, Matthew, and 

 Beecher, which enabled them to give a somewhat definite account of 

 the appendages and antennae of these extinct Crustacea. Dr. Beecher 

 has followed up his account by two more papers, the first of which 

 (Avierican Geologist, January, 1894) deals with" the mode of occurrence, 

 and the structure and development of Tnarthrus becki, and is founded 

 on specimens obtained from the Utica shale (?) of Rome, New York. 

 In this paper the definite structure of the legs of the thorax has been 

 worked out in detail, and shows each limb to consist of " two nearly 

 equal members, one of which was evidently used for crawling, and 

 the other for swimming." " Each limb is composed of a stem, or shaft, 

 with an outer branch (exopodite), and an inner branch (endopo- 

 dite)." "The precise form of the coxal joint of the stem (coxopodite) 

 has not yet been clearly made out. It is followed by a broad joint 

 about twice as long as wide, which may be referred to the proto- 

 podite." Dr. Beecher says : " The final conclusions to be reached 

 from a complete study of the development and structure of these 

 animals can only yet be surmised. It is quite evident, however, 

 that they are related to the true Crustacea." 



In the second paper {Amer. Journ. Set., April, 1894) the structure 

 of the appendages of the pygidium of Triarthrus becki is shown to be 

 as follows : " The endopodites preserve their slender, jointed distal 

 portion, but the proximal part is composed of segments which are 

 considerably expanded transversely, thus making a paddle-like organ, 

 the anterior edge of which is straight, while the posterior one is 

 serrated by the projecting points of the expanded segments. These 

 points bear small bundles of setae." 



An Eocene Pteropod. 



The identification of a Pteropod in British Eocene strata is of 

 considerable interest, when we remember that no less than six species 

 are known from similar beds in the Paris basin. Mr. G. F. Harris gives 

 a description and a figure of the new form, which he names Euchilotheca 

 elegans, in the Proceedings of the Malacological Society (vol. i., no. 2). 

 The specimen is incomplete, was found at Bracklesham, and belongs 

 to the well-known Edwards Collection in the Natural History Museum. 

 In the same journal, Mr. R. B. Newton redeems in part a promise 



