from Tipper Silurian, New South Wales. 339 



Jaws of Annelids. PL XT. Figs. 6-10. 



Originally described by Dr. Pander in 1856 in connection with the 

 fish remains of the Russian Baltic Silurian, these bodies have now- 

 been satisfactorily shown by Dr. G. J. Hinde to be the horny jaws 

 of Errant Annelids. Their intermediate history has been so fully 

 treated by this author in his papers mentioned below, 1 that it is 

 quite unnecessary to enter into the subject. It is now sufficient to 

 state that these little bodies have been found in strata ranging from 

 the Cambro-Silurian to the Carboniferous, and it is stated by Dr. 

 Hinde that they "occur as small dark shining objects, very varied 

 in form, dispersed through the rock, quite detached from each other, 

 and from the positions they occupied in the head of the animal. 



Except in cases where they have been long exposed to 



weathering influences, the jaws are of a bright glossy black tint." 



Dr. Hinde further adds that the size of the jaws varies between 

 -iV and 3- of an inch in length ; that their resemblance to the 

 masticatory organs of i*ecent Annelids is very striking; and that 

 so far as his researches have extended, three families are represented 

 in Palasozoic rocks — the Eunicea, Lycoridea, and Glycerea — the first 

 containing the largest number of forms. 



In the case of the Australian jaws precisely the same general 

 description applies. Three form-? of jaws have so far been obtained 

 by Mr. Mitchell, with a number of other indeterminable fragments. 



Form 1. — A jaw plate (Figs. 6, 7, and 10) composed of a hori- 

 zontal ramus, terminating anteriorly in a little curved short hook, 

 blunt, and possessing a general average length of two mm. There 

 are no perceptible denticles, so far as observation has gone, whilst the 

 posterior end is excavated into a V-shaped notch. This so mani- 

 festly recalls some of the non-dentate species of Eunicites figured by 

 Hinde, that I include it in this genus as E. Mitchelli. It does not 

 closely appi'oach any of the species given by this author in its more 

 minute detail, nor does it exhibit the same curvature or conical 

 section of the bodies figured as the pincers of Eunicites from 

 Gotland, 2 although this may be only the result of pressure perhaps. 



Form 2. — The jaw-plate in this variety (Fig. 8) is much elongated, 

 the upper and lower margins sigmoidally curved, terminating for- 

 wards in a rather long attenuated hook, which is inclined to the 

 ramus at first nearly at right angles, and almost in the same plane. 

 The superior margin is occupied by a series of small denticles, 

 greatly disproportionate in size to the anterior hook, about eight to 

 ten in number, and apparently placed on a flattened border. Imme- 

 diately below the denticulate margin is the most prominent and 

 convex portion of the plate, followed below by a concavity, extend- 

 ing along the central part of the plate. This form (Fig. 8) seems 



1 On Annelid Jaws from the Cambro-Silurian, Silurian, and Devonian Formations 

 in Canada, and from the Lower Carboniferous in Scotland, Q. J.G.S. 1879, vol. xxxv. 

 p. 370, t. 18-20. 



On Annelid Remains from the Silurian Strata of the Island of Gotland, K. 

 Svenska Vet.-Akad. Handlingar, 1882, vii. No. 5. 



2 K. Svenska Vet.-Akad. Handlingar, 1882, vii. no. 5, t. 1, f. 1-5 {separate copy). 



