292 
SUPPLEMENT TO THE BRmSII 
they do not appear to pass to the outer surface of the shell. They are also seen in the 
variety /S. distorta. 
Vascular impressions. — At p. 77, and in pi. xx of his ' Monograph of Permian Fossils 
of England,' 1850, Prof. King describes and illustrates the vascular systen) as seen on 
the interior surface of both valves of Stroplioriiena analoga, stating, at the same time, that 
the pallial vessels run parallel with each other till they have reached the anterior 
region, where they sweep round submarginally on both sides, giving off a series of 
smaller vessels. In the General Introduction to Vol. I of my work, and in my Carbo- 
niferous Monograph, I give additional illustrations which, in every respect, agree with 
those figured by Prof. King, and show that the outer principal vessels occupy the 
longitudinal median portion of the valves, surround the ovarian spaces, and give off 
smaller bifurcating vessels (Carb. Mon., PI. XXVIII, figs. 9 — 11). That this description 
and Prof. King's, and my own illustrations, are correct is amply proven, and so recognised 
to be the case by Dr. S. P. Woodward, Mr. J. Young, and others. 
Quite recently, however, while examining some internal casts or decorticated examples 
of Strophomena analoga from the Carboniferous Limestone of North Hill, Campsie, near 
Glasgow, Mr. John Young was surprised to find that the vascular impressions in two or 
more specimens did not exhibit those vessels in the manner described by Prof. King and 
myself, that they pursued quite a different course, and did not form a ring round the 
ovarian spaces, nor did they show that they sprung from any main trunk vessels, but that 
they passed simply out from the median region and radiated over the whole interior 
surface of the valves ; that the vessels kept nearly of a thickness throughout their whole 
course, and that, if each vessel is carefully followed from the anterior front margin of the 
shell, they will be seen to converge in a radiate manner to near the central portions of 
the beaks of the shell (Sup., PI. XXXVI, fig. 23). 
How to explain this marked divergence from the general plan observable in so many 
specimens has puzzled, and still puzzles, both Prof. King, Mr. J. Young, and myself. 
These differences are evidently not due to age, for in both cases do we find this difference 
to occur in middle-sized and adult individuals. Several decorticated examples of 
Str. analoga, var. distorta, from near Carlisle, have shown the same peculiarity. 
Genus Orthis, Balman. 
32. Orthis Michelini, rEveille. Dav., Carb. Mon., p. 182, PI. XXX, figs. 6—12 ; 
Sup., P]. XXXIV, figs. 15—17. 
In a paper by Captain R. Brown, entitled " Descriptions of some new species of 
Fossil Shells found chiefly in the Vale of Todmorden, Yorkshire " (' Transactions of the 
