SACCOCARIS MAJOR. 85 



of the curvature being above the mesial line, thus making the antero-dorsal much 

 shorter than the antero-ventral curve. 



Apparently blunt or truncate behind, with a gentle outward curve rather 

 above the middle. The exact line of this posterior margin is not clearly seen, 

 owing to its passing into the substance of the black schistose mudstone, the valve 

 having been dehcately plaited (with the stone), and gently undulate throughout, 

 in lines parallel to the long axis of the valve ; and pressure having acted at 

 right angles to its length, this longitudinal plaiting (pleating) is transverse to 

 the hind border, and the whole surface is compressed and corrugated from edge 

 to edge. The hinder margin of the valve, indeed, is barely perceptible, having 

 been shredded or frayed off by its extremely plaited state, or, in other words, 

 frittered away in longitudinal shreds parallel with the plaiting of the rock, showing 

 probably that this end was of thinner consistence than the rounded front edge, 

 which has not been affected nearly so much, having probably been thicker, or 

 even slightly rimmed. 



This frayed condition often occurs with the ends of phyllopodous specimens in 

 the Lingula-flags. There are also some irregular concentric lines in the antero- 

 ventral area of the specimen, caused by depression in the convexity of the valve. 

 By the cross-pressure the specimen must have lost something in height, and has 

 had its length exaggerated. 



The valve, slightly hollow, is probably the right-hand valve, showing its 

 inside. Several concentric, irregular, narrow foldings, following the contour of 

 the anterior and antero-ventral border, are apparently due to the compression of 

 the convexity of the valve. 



This specimen. No. 1 at p. 220 of the First Report, and fig. 1, p. 178, Report 

 for 1888, is marked ywo^ tWj in the Woodwardian Museum of the Cambridge 

 University, and was collected by Mr. D. Homfray from the upper part of the 

 Lower Lingula-flags at Cae'n-y-coed, near Maentwrog. 



This was at first (in 1867) regarded by Mr. Salter as a flat carapace, " after 

 the manner of Ajjus ;" but afterwards (in 1873) he referred it to the bivalved, 

 folded, or Nebalioid forms of carapace, and placed it as an ally of Hijmenocaris, 

 with the name Saccocaris. In shape it differs much from the valves of that genus, 

 as it wants their triangular form, due to the dorsal line forming an angle with the 

 front edge, which slopes rapidly downwards and backwards all along the ventral, 

 to join the posterior margin, with a bold, oblique postero-ventral curve. Difi"ering 

 also remai'kably in size, it must be assigned to a different generic group, and we 

 thought it best to recall the name which Salter was at first inclined to give it, 

 namely Saccocaris. 



We have met with no evidence of the body-segments alluded to by Mr. Salter, 

 nor are the " three distinct ridges on the hinder border" recognisable. On the 



