30 ME. J. CA.ETEE OlSr THE PAL.^OKTOLO&Y OF [Feb. 1 898, 



region rather less than half the greatest width of the carapace. 

 Rostrum widely bifid, with elongated lateral spines. Orbits opening 

 forward ; npper border with two distinct lobes, which are separated 

 from each other by a deep sinus and from the external orbital lobe 

 by a sharp fissure ; external angle of orbit much produced, extending 

 nearly as far forward as the rostral spines. The antero-lateral 

 border, in addition to the external orbital spine, bears four other 

 well-developed acute processes. Postero-lateral margin nearly 

 straight, inclining inward and rendering the posterior about equal 

 to the orbito-frontal border. A distinct sinuous cervical sulcus 

 marks off the anterior third of the dorsal area from the scapular 

 portion. Gastric regions obscurely indicated. Branchial regions 

 sharply defined ; the epibranchial terminates about midway between 

 the margin and the median dorsal ridge, and is separated from the 

 mesobranchial lobe by an undulating sulcus ; a similar and nearly 

 parallel groove — the inner half of which is obliquely crossed by a 

 series of interdigitations — divides the meso- from the metabranchial 

 lobes. A granulated longitudinal ridge, slightly inflected in the 

 middle, carinates each metabranchial lobe, and a median carina 

 extends the whole length of the carapace. Of the faintly-marked 

 areolar tubercles, two occur on the protogastric and three or four 

 on the median ridge. Length of carapace = 31 mm.; width (not 

 measuring marginal spines) = 44 mm. 



.Affinities. — In general form this species closely resembles Necro- 

 carcinus tricarinatus, but it difi"ers from all the species of Necro- 

 carcinus in the structure of the rostrum and in the conformation 

 of the orbital regions, as also by the greater development of the 

 spines ^ of these antero-lateral margins. 



The characters of the carapace indicate an affinity, as Dr. Wood- 

 ward has remarked, rather with the Portunidge than with the 

 Corystidae. The orbito-frontal characters are very similar to those 

 of Orithyia ; but the armature of the antero-lateral margin, 

 especially the well- developed metabranchial spine, approximates 

 to that in Matufa. The zoological position of OritJioj)sis appears 

 to lie between these genera. 



Distribution. — Upper Greensand, Lyme Regis, and (?) Isle of 

 Wight; Gault of Folkestone. I have seen fifteen specimens, which 

 are preserved in the British Museum, the Museum of Practical 

 Geology, the Woodwardian Museum, and my own collection. 



Genus Campylostoma, Bell. 



Campylostoma matutieoeme. Bell. 



1858. Bell, Monogr. pt. i, p. 23 & pi. iii, figs. 8-10. 



Sup]plementary . — Granules occupy the sulci and obscure the 

 outline of the normal lobes. Orbito-frontal margin nearly equal to 

 half the width of the carapace. Orbits large, transversely oval, 

 opening obliquely upward ; the margin thin, divided into fiattened 



^ These are more slender than represented by the figure in the Geol. Mag. 



