Victorian Fos;sils, Fart X. 103 



majority of the Victorian fossils of the above genus belong to 

 a type characterised by a tubular covering thicker than that in 

 the English examples, in which the tubes were typically mem- 

 branous and thin. That these fossils may with good reason be 

 regarded as the crypts of burrowing worms, is shown by the 

 form and disposition of the tuloes in the surrounding matrix, 

 which, with their solid infillings, traverse the bedding planes 

 at all angles, but are usually inclined from 20-45 deg. Several 

 specimens have Ijeen collected by Mr. Spry which show a vertical 

 direction of the tube at the commencement, but soon after 

 change to the oblicpie position, and continue meandering for 

 some distance ; the longest specimen found, up to the present, 

 measuring a little more than 10 cm. This habit of passing 

 downwards through layers of the soft black or grey mud (shale)^ 

 suggests an affinity with the burrows of such of the polychaetes 

 which secrete a parchment-like tube. Any reference to the 

 s.edentary worms, like the Scrpulidae, as suggested by Phillips, 

 is untenable, since the buried tip or termination is completely 

 and evenly rounded, as shown in Plate XXTX.. Fig. 1 ; whilst the 

 sides of the tubes are often irregularly and quite suddenly 

 constricted, instead of gently tapering, as in most so-called 

 sedentary forms. 



Tpachyderma crassituba, sp. nov. 

 (PI. XXYIL, Figs, la, lb, 2, 3, ?(4); PI. XXIX., Fig. 1). 



Description. — Tube comparatively thick. Near the entrance, 

 the burrow is usually quite cylindrical, but becomes elliptical in 

 section in its oblique course through the shaley mudstone ; long 

 and slightly tapering, with rounded extremity. Externally the 

 tube is marked with coarse corrugations or annuli. Internal 

 surface of tube and casts of the interior are closely ornamented 

 with annulate striae, sometimes disposed obliquely and often 

 imbricated. Sides of tube bulging at intervals ; occasionally 

 the whole tube is arcuately bent. Interior of tube filled with a 

 solid core of hard mud, frequently arenaceous, and stained with 

 carbonaceous or organic matter. 



Dimensions. — Length of tube in the holotype, cir. 100 mm. ; 

 width, 16 mm. : thickness of tube, cir. 4 mm. 



2.4 



