132 BRITISH PALAZOZOIC FOSSILS. [AnnuLata. 
2nd Tribe. AMPHITRITZ. 
Tube fragile, straight or gently curved, unattached, formed either of naked membrane alone, membrane 
with grains of sand, &¢. agglutinated, or solidified by a small proportion of calcareous matter, forming a 
dense thin, smooth, glossy tube. Marine, 
Genus. SERPULITES (AMurch.) 
Gen. Char.—Tube smooth, arched, slightly calcareous, glossy; having two small longitudinal tubes at 
opposite points of the circumference (the convex and concave faces of the curve), stronger than the rest 
of the shell, and prolonged at the posterior end. 
SERPULITES DISPAR (Salt. in App.) PI. 1. D. fig. 11, 12. 
Sp. Ch.—Upwards of four inches long and two lines wide in the greater part of its length, slightly 
curved, rather rapidly tapering towards the small end; extremities unknown ; two lateral tubules very strong, 
calcareous, one-third of a line in diameter, intervening portion of tube very delicate, nearly membraneous. 
The small diameter, and the exceeding delicacy of the sides of the tube compared with the strength and 
hardness of the two lateral tubules, easily distinguish this species from the S. longissimus (Murch.) Not 
unfrequently the delicate membraneous portion disappears, leaving a very puzzling appearance in the two 
disconnected wire-like lateral tubules. 
Position and Locality.—Abundant in the Upper Ludlow rock of Scalthwaite Rigg, N. end of Benson 
Knot, Kendal, Westmoreland; in the calcareous flags of Dinas Bran, Llangollen ; N. end of Tenter Fell, 
Kendal. Single lateral tubules apparently of this fossil occur in the black shale at three miles N. of 
Builth, Radnorshire; in the fine greyish sandstone of Tan y Craig, Builth; in the sandstone of the 
Hollies, Church Stretton, Shropshire. 
Explanation of Figures —P\. 1. D. fig. 11. Natural size from Benson Knot.—Fig. 12. Ditto. 
SERPULITES LONGISSIMUS (Murch.) 
Ref.—Murch. Sil. Syst. t. 5. f. 1. 
Sp. Ch.—Subcompressed tube upwards of a foot long, gradually tapering at the rate of only two lines 
in five inches, forming part of a curve about one foot in diameter at the large end, but curving more 
rapidly towards the apex; surface with obtuse transverse undulations ; shell thin, glossy, opaline ; average 
diameter four lines, of thickened convex and concave margins nearly one line. 
Position and Locality—Common in the Upper Ludlow rock of Aymestry, Herefordshire. 
Genus. TRACHYDERMA (PaAill.) 
Gen. Char—Tube submembraneous, tough, flexible; surface with short irregular transverse wrinkles 
or plaits. 
This genus has been proposed (Mem. Geol. Surv.) by Prof. Phillips for some large, cylindrical, variously- 
curved coriaceous tubes of the Upper Silurian rocks, with an irregular, sharp, transverse plication of the 
surface ; this latter character is so variable, and obviously unimportant, that by extending the genus so as 
to include all the simple submembraneous naked tubes of the Silurian rocks it would be more useful and 
intelligible, being distinguished from Serpulites by the latter having two strong lateral tubules, which I 
have shewn (Synopsis of the Carboniferous Fossils of Ireland, p. 170) to be highly characteristic of that 
genus, although it seems not to have occurred to the Survey observers as a distinctive character. 
