BIHANG TILL K. SV. VET.-AKAD. HANDL. BAND 7. N:0 5. 7 



A glance at the forms representpd on thc plates will at 

 once shoAv how greatly these Gotland annelid remains resemble 

 those from tlie Silurian and Devonian strata of North America 

 and England, -wliich I have described and figured in tlie Quar- 

 terly Journal of tlie Geologieal Society for 1879 and 1880. 

 The majoritj of the specimens can be placed in the same 

 species ; others differ in small details of structure, whilst there 

 are a few distinctive forms, which appear here for the first 

 time. On the whole the Gotland examples are decidedly 

 smaller than those from England and America. The largest 

 specimen which I have discovered is scarcely 2 mm. in length, 

 whilst the smallest jaw plates do not exceed 0,3 mm. On 

 comparing the figures accompanying this paper, with those 

 of my previous papers, it will be necessary to take into ac- 

 count the much larger scale to which the former have becndrawn, 

 for in order to convey a just idea of the relative dimensions, 

 and to allow of adequate representation of the smaller forms, 

 I have delineated them all on the same scale of 28 diameters. 

 The Silurian Annelids, if one may judge from a comparison of 

 their jaw plates with those of existing Errantia, would not have 

 been more than 7 to 10 cm. in length, and thus perhaps of nearly 

 corresponding dimensions, or, if anything, rather smaller, than 

 the majority of the existing commoner forms of the order. 



The freedom from the matrix, and the perfect preserva- 

 tion of these Gotland examples afford greater facilities for ma- 

 king a comparison with the jaw apparatus of existing annelids 

 than could have been obtained from the American and Eng- 

 lish specimens, which had, as a rule, but one surface exposed. 

 The Gotland examples exhibit both the upper and under sur- 

 faces, so that it is possible to ascertain the characters of both 

 in the same specimen. 



Scarcely a doubt can be entertained that these various 

 fossil jaw plates, with one or two exceptions, belonged to 

 Annelids whose nearest representatives in the existing seas 

 are comprised in the family of the Eunicea. Such is the 

 opinion which Prof. Ehlers, the principal authority on living 

 Annelids, has communicated to me after an examination of 

 some of the Gotland specimens which I submitted to him. 

 This family of the Nereidea, as is well known, is distinguished 

 from the other allied families of the order by the possession 

 01 a jaw armature consisting of several distinct chitinous 



