Prof. W. B. Benham — A Giant Fossil Cirrijjede. 113 



a rough but definite edge is here formed. The breadth of the 

 tectum remains nearly uniform over the lower half, but widens very 

 slightly near the middle ; it then diminishes very gradually towards 

 the distal portion ; although the apex is absent, it was probably 

 about half the breadth of the base. The lines of growth are 

 practically transverse, and, as frequently is the case, those near the 

 middle are more widely spaced than at the proximal extremity, 

 where they are rather oblique. 



The parietes are nearly complete, but are partly broken away 

 near the distal extremity. Seen laterally, each parietes is practically 

 a triangle, with a very long curved base, attached, of course, to 

 the margin of the tectum. The lower or proximal side of the 

 triangle is longer than the distal, and is slightly excavate, i.e. it is 

 not a straight line. The distal side, as far as can be judged, is 

 a straight line ; what is left of it appears to be uninjured. The 

 lines of growth on each parietes are very close set ; starting from 

 the basal extremity they at fi.rst run nearly straight, but slightly 

 obliquely, upwards ; then, where the flange widens out, they curve 

 outwards and bend abruptly backwards, terminating along the 

 distal side of the triangle. There is thus left a small smooth 

 ' bay,' triangular in form, on the proximal side of the apex. 



There is no ridge, but the surface suddenly drops along the line 

 of junction of tectum and parietes ; the angle formed by each of 

 the latter with the former is about 135°. 



The upper end of the valve is broken, but if the tectum be 

 produced to meet the production of the distal side of the triangular 

 parietes, the point of union will add about 25 mm. to the total length 

 of the carina. 



The inner surface of the valve is, in its upper half, marked by 

 a series of fine transverse ridges and furrows ; at the actual point 

 of bending there is a narrow and well-defined ridge, while below^ 

 the surface is smooth. 



The following measurements were made : — 



mm. 



Length of fragment 133 



Probable total length about 160 



Greatest breadth of tectum 18 



Breadth at base ... ... ... ... ... ... 15 



Breadth at fractured end ... ... 10 



Thickness 2 



Parietes — greatest breadth 25 



(&) The Scutum. (PI. IX, Figs. 1-2.) 



This valve is 7^ inches in length, and only 1^ in breadth ; it is 

 thus remarkably narrow in proportion to its length. It will be 

 convenient to distinguish a ' main plate ' from a ' flange ' which 

 exists on one side, and is scarcely seen when the valve is looked 

 at squarely from above ; this ' flange ' is the greatly inflexed latero- 

 tergal region of the valve, which is set on to the ' plate ' at an angle 

 of about 115°. The ' main plate ' is almost complete. There appears 

 to have been a small apical region broken or worn away ; but apart 



DECADE IT. VOL. X. NO. III. 8 



