54 PEOCEEDINGS OF THE GEOLOaiCAL SOCIETT. 



eyes or facial suture. Only two, instead of fourteen, body- rings 

 are visible ; and these, as well as the head, are crowded with those 

 characteristic tubercles which are so common in embryo forms of 

 this group, and which indeed are retained long after in certain 

 species and genera. The tail is of the ordinary type, a good deal 

 developed for the size of the animal, and marked vrith two or three 

 distinct segments, tubercular like the rest. 



In these young forms it is impossible not to see the representatives 

 of genera such as Agnostus, which has two, and Microdiscus, which has 

 four rings in the adult state. The cylindrical unfurrowed glabella and 

 the want of eyes, the few body-rings and the great relative develop- 

 ment of the tail, are as conspicuous in the embryo of Conocoryjyhe as 

 in the adult state of the humble forms above quoted. What is the 

 precise nature of the tubercles which are so conspicuous in the em- 

 bryo of Sao, for instance, as given by Barrande, it is difficult to 

 say. I have called attention to them elsewhere. — Mon. Pal. Soc. 

 Trilobites. Monograph, pt. 1 (under Phcicops), pi. 3, p. b2.- — J. W. S. 



Locality — " Menevian Group," Porth-y-rhaw, St. Da\id's ; also 

 near Maentwrog and Dolgelly, North Wales. 



3. CoifocoEYPHE (?) HtTMERosA, PI. II. fig. 7. Salter, Brit. Assoc. 

 Report, 1865, p. 285. 



Of this curious species, a part of the head and six thoracic rings 

 only have been found. These, however, show characters sufficiently 

 marked to indicate that it is specifically (if not generically) distinct 

 from either of the others. 



The glabella is large and elongated, reaching apparently to the 

 frontal margin, not furrowed, but sharply ridged centrallj'-, separated 

 from the cheeks by very deep dorsal furrows. Cheeks narrow, con- 

 vex, and acutely triangular, surface smooth, with no trace of ocular 

 ridges, or facial sutures, or of being strongly marginate; a very 

 strong spine occurs on the neck segment. 



The thoracic axis is highly convex, and spinous along the centre ; 

 the pleurse are wide, very deeply furrowed, and terminate in long, 

 tapering spines, which curve sharply backwards ; the fulcrum of the 

 pleurae occurs about midway from the base of the spines to the axis. 

 The pleurae, without the spines, are only a little longer than the 

 width of the axis, and bend sharply at the fulcrum. 



Locality. — " Menevian Group " (middle beds) Perth -y-rhaw, St. 

 David's. 



4. Paradoxides Atjeoea, Salter, PI. II. figs. 9-12. Brit. Assoc. 

 Eeport, 1865, p. 285. 



A few rather imperfect heads, some loose free cheeks, and un- 

 attached pleurae only have as yet been found ; but these are suffi- 

 cient to indicate a new and very distinct species. Its position, also, 

 in the grey rocks, at the very base of the " Menevian group'' renders 

 it a most important species, and necessitates its description even in 

 this imperfect state. 



