Vol. 51.] ANNIVEESAEY ADDEESS OF THE PEESIDENT. lxxix 



previous knowledge derived from the important researches of 

 C. D. Walcott, he proceeds to describe the additions which the 

 specimens from Rome have supplied. These trilobites are found in 

 a soft, fine, black shale, and are perfectly well preserved. The 

 most noticeable character is the presence of long, slender, many- 

 jointed whip-like appendages attached to the front of the head, 

 closely resembling the flagellate antennae of other crustaceans. 

 These originate close together, just beneath the centre of the 

 anterior border of the head-shield, and are as long again, nearly, 

 as the glabella itself. Mr. Matthew also was able to detect a series 

 of walking- or swimming-legs, one a narrow, jointed, cylindrical 

 leg, the other thin, broad, fringed with a comb-like structure similar 

 to the gills of many Crustacea. 



The next communication is from Mr. C. E. Beecher, of New 

 Haven, Conn., ' On the Mode of Occurrence and the Structure 

 and Development of Triarihrus Becki.' 1 The material gathered for 

 the Yale University (by the aid of Prof. Marsh) near Eome, New 

 York, is probably some of the best which has been obtained, and 

 has been carefully examined and described by Mr. Beecher. 



In their present condition the specimens from Borne contain very 

 little calcite, nearly the entire calcareous and chitinous portions of 

 the trilobites being replaced by a thin film of iron pyrite. To this 

 cause is doubtless due the preservation of delicate organs and 

 structures which would otherwise have been destroyed. 



The specimens thus preserved occupy an extremely restricted 

 vertical distribution, but within this range they are nearly all 

 complete and preserve their appendages. They are of all ages, from 

 larval forms up to full-grown individuals, whilst the adjacent strata 

 contain a rather sparse fauna in which the trilobites are generally 

 fragmentary and without appendages. The author believes that, 

 in the majority of beds in which trilobites are found, the remains 

 met with represent the exuviae of living animals that have cast 

 their shell, rather than the tests of dead individuals. In this 

 particular deposit the appendages are apparently in the position which 

 they occupied during life, and not such as would be assumed in the 

 cast-off shells of recent Crustacea. 



Mr. Beecher mentions another interesting point, namely, that 

 nearly all the specimens are found with the back down, which is 

 explained by suggesting that, although they lived with the ventral 



1 From the 'American Geologist,' vol. xiii. (January 1894) pp. 38-43, 

 pi. iii. 



