238 



MESSRS. PEACH AND HOENE ON THE 



The visual portion of the eye occupies the greater part of the steep 

 outer edge of the crescent, and though no actual remnant of the visual 

 membrane has been preserved, the place it once occupied is repre- 

 sented by a narrow crescent-shaped slit with rounded extremities, 

 which describes a curve of about one third of a circle. This is 

 margined by a thickened ridge or pseudo-palpebra. The inner or 

 anterior canthus of the eye is a little wider and more rounded than 

 the outer or posterior. The eye-lobe and the edge of the glabella 

 almost enclose a portion of the test which stands up in the form of 

 a gently-swelling elongated boss. No trace of a facial suture is 

 observable on the dorsal aspect of any carapace that we have 

 studied. 



On the underside of some specimens the doublure is shown and is 

 always a little wider than the dorsal marginal ridge. The suture 

 along the external edge of the doublure has not been observed, but 

 this may be because the specimens are not sufficiently well preserved 

 to show it. No trace of the facial suture has been found where it 

 cuts the posterior margin in Paradoxides, though the specimens were 

 favourable for its observation. The hypostome has not been observed. 



A table of ^neasureraents of severed carapaces of 0. Lapworthi 

 here given to slioiu the amount of variation in form : — 





M 

 2473d, 

 fig. 1. 



M 



2468'', 

 fig. 2. 



Sg. 1. 

 fig. 3. 



M 



2472<i, 

 fig. 4. 



M 



2476", 

 fig. 7. 



M 



2502d. 



Length along middle line . 

 Breadth just in front of 



genal spines 



Distance between inner 



canthus of eyes 



mm. 

 16 



28 



8 



11 



1-25 

 •45 



mm. 

 16-5 



35 



10 



14 

 10 



1-5 



1 



mm. 



18 



40 

 11 

 12 



3 

 ] 



ram. 

 15 



25 



5 



8 

 8 



2 



1-5 



mm. 

 9 



18 



mm. 



8 



14 



Distance between outer 

 canthus of eyes. 



Length of genal spine 



Breadth of margin in front 

 of genal spine 



Breadth of margin near 

 middle line 





The figures at the top of the columns in the above table apply to the numbers 

 of the specimens in the books of the Geological Survey of Scotland. 



Though no body-segment has been found attached to any one of 

 the numerous carapaces, yet the presumption is in favour of the 

 opinion that the remains of segments and the telson already men- 

 tioned belong to this species. 



The first or second body-segment (PI. Y. fig. 9) consists of a 

 central lobe 7 mm. wide by 1-5 mm. deep. The left pleuron is best 

 preserved, aud is 8 mm. by 1-5 mm. deep. It is continued in the same 

 straight line as the axis of the central lobe, and is strengthened on 



