A. H. Honvood — Arcliarenicola Rhmticn. 395 



II. — On Aechabenicola Rhmtica^ sp. nov. 

 By A. E. HOEWOOD (Leicester Museum). 

 (PLATE XXI.) 

 GrENEEAL Notes on the Hoeizon of Specimens A and B. 



IN the latter part of 1910 I was agreeably surprised upon the 

 examination of some material from the Rhaetic Black Shales at 

 Glen Parva, Leicestershire, to detect a specimen which at the moment 

 I recognized as new (specimen A). 



Reference to this discovery, and to that of a second example in the 

 Museum collections (specimen B), has already been made in brief in 

 the hope that, if other material of the kind existed, I might be 

 apprised of it. So far, however, no further specimens have been 

 obtained. 



Specimen A, upon which I found the type, was not found in situ, 

 but the burrows which undoubtedly belong to it are commonly found 

 at 1 to 2 feet above the bone-bed, here the base of the Bhsetics, 

 overlying Tea-green Marl. 



Specimen B was found by me amongst some old material in this 

 Museum, which I have every reason to believe came from the now 

 covered-up exposure of Rhsetic beds at Spinney Hills, reported by the 

 late Mr. W. J. Harrison, F.Gr.S., a former curator.^ This specimen 

 came from the bed numbered 5 in the section given, ' ' sandstone 

 1 inch." On the other side are broken shells of Avicula contorta. 



Review of Geouping of Fossil Polych^tes. 



Amongst Possil Annelids so far only traces of Marine Polychaetes 

 have been detected. These have been subdivided into two groups — 

 («) Tubicola (Sedentaria), in which the parapodia are short and not 

 used for swimming and in which the animal lives in a tube ; 

 {h) Errantia (Nereidse), in which the animal is free-swimming and 

 has a well-marked head, well-developed parapodia, with setse used 

 for locomotion. Some forms included here possessed powerful jaws. 



There are really no authentic Palaeozoic impressions, since those 

 included in Nereites^ Nemertites, Myrianites, Nemapodia, Crossopodia, 

 Phyllodocites, Naites, etc., have been regarded as due to movements 

 of Crustacea, Annelids, Gasteropods, and are not impressions of the 

 cuticle at all.^ This being so, the impressions here described must be 

 regarded as belonging to a new order, and they belong to a diiferent 

 group, or Arenicolidse. 



The burrows included the genera Scolithus, Arenicola, Histioderma, 

 PlcmoUtes, Biplocraterion, Sjnrocolex, Scolecoderma, some of which 

 were described or grouped by Nicholson.* He considered, as did 

 Nathorst, some of the trails or tracks were perluips formed by Annelids, 

 Crustaceans, or Molluscs. 



^ Eep. Brit. Assoc. Portsmoutb, Trans. Sections, 1911. 



* " On the occurrence of Ehastic Beds in Leicestershire " : Q.J.G.S., 1876, 

 p. 212. 



^ A. G. Nathorst, " On the Tracks of some liivertebrate Animals and their 

 Palseontological Significance" : K. Svensk. Vetensk. Akad. Handl., Bd. xviii, 

 xxi, 1881-6. 



■* H. A. Nicholson, " Contributions to the Study of the Errant Annelids of 

 the Older Paljeozoic Eocks " : Proc. Eoy. Soc, 1873, p. 288. 



