10 



PAL/EONTOLOGY OF NEW YORK. 



of Wisconsin.* Upon the first plate of this volume are given, in addition to 

 copies of the figures named, a number of illustrations representing these impres- 

 sions in different degrees of completeness; especial attention may be directed 

 to the figures of L. punctata, L. Proderi, L. densa, and to those of L. lamellata, 

 upon Plate IV k. (See, also, the figures of L. Lewisi, Sow., given by Davidson,! 

 and the accompanying text illustrations of extremely well preserved internal 

 casts of L. Metie [brachial valve], and L. paracletus, sp nov. [pedicle-valve].) 



There has been a considerable diversity of opinion among authors, in regard 

 to the special functions of the various muscular bands in Lingula. Few in- 

 vestigators have brought to the study of this subject the clear insight and 

 incisive judgment of Professor William King, whose nomenclature of the mus- 

 cles, we have preferred to adopt. 



The first strong impression arising from the comparison of these ancient forms 

 with the type-speciesis that in the former, the dorsal scars of the centra/ muscles (A) 

 are relatively much the larger, and 

 are situated somewhat posteriorly, 

 apparently encroaching upon that 

 portion of the visceral chamber 

 which, in L. anatina, is occupied 

 by the essential organs of the 

 animal. This apparently great 

 size, however, is somewhat illusory, 

 as undoubtedly a portion of these 

 large scars is due to their contin- 

 ued advance as the shell increases 

 in age, and probably at no time in 

 the mature life of the animal did 

 these muscular bands, at their or- «"!?«?« afwwna, ancr Davidson. 



Fig. 6. Pe(licle\alvo. FIG. 7. X Brachial valve. 



igin and insertion, cover the entire '■ Pa"e'»l fV',; S. umbonal muscle; », transmedians. A, centrals; 

 o ' wiv^v,ni,ii^ .J, e.t, laicrals (J, aiilcnors; i, middles; J, externals). 



* Viil. iv, p. 3-l.'i, jd. xxvii, tigs. 3-.'). 18S2. 



t Monogr. Brili.sh Silurian Bracli., pi. iii, fig-s. 5, G. 



J DAvrD.soN'.s tijfuies are iliafjnimmatii' copies of the more elaborate illustrations given by King. In the 

 process of copying' it is evident that fig. 7 has been revei-sod, and the position of the double and single 

 muscular bands of (i) inverted. 



