ASAPHUS. 147 



tail with many ribs on axis and limb ; facial suture marginal in front ; hypostome^ entire. 

 Labrum deeply lobed. Mange. — North and South Europe. 



Types, A. tyrannus, Murch. 

 A. Powisii, Murch. 

 ? A. ingens, Barrande. 



3. Megalaspis, Angelin, 1852. Flattened and expanded, with narrow axis; short 

 urceolate glabella, reaching but a little way up the head, and lobeless ; approximate 

 depressed eyes, subangular tips to pleurse ; and tail with narrow long axis, and many ribs 

 on axis and limb. Facial suture intramarginal, in a long ogive on the upper surface. 

 Hypostome — ? Labrum notched ? North Europe. 



Angelin figures a labrum of M. planilimhata as entire, but there is some imperfec- 

 tion in the look of the figures, as if the forked lobes were broken off. 



Types, A. gigas, Angelin, not of Dekay. 

 A. heros, Daltn. 

 A. extenuatus, Dalm. 

 A. nohilis, Barr. 



[1 have inserted here A. nobilis, Barrande, chiefly to call attention to it. It is possibly 

 a distinct subgenus. Its short glabella is lobed posteriorly ; the hypostome appears to have 

 a vertical suture ; the pleurae are recurved and pointed ; the tail-furrows not duplicate ; 

 and the crust very thin. It seems intermediate between Basilicus and Megalaspis?^ 



4. Isotelus, Dekay, 1824. Convex, moderately expanded, with broad axis; obsolete 



glabella; remote, moderately convex eyes; rounded pleurae, and no ribs on the tail. 



Facial suture intramarginal, ogived. Hypostome vertically divided. Labrum deeply 



furcate. North America, North-west Europe. 



Types, I. gigas, Dekay. 



/. platycephalns, Stokes. 



5. Cryptonymus, Eichwald, 1825. Hemicrypturus, Corda, Asapkus, Angelin. Short, 

 convex, with narrow axis, a clavate glabella reaching the front of the head, and with three 

 pairs of lobes ; elevated eyes (sometimes stalked in the $ ) ; rounded pleurae ; tail short, 

 of few joints, very obscurely ribbed, except on the axis. Facial suture intramarginal in 

 a short ogive. Labrum deeply lobed. North Europe. 



Types, A. expansus, Linn. 

 A. raniceps, Dalm. 



6. Symphysurus, Goldfuss, 1843.^ Short convex, with narrow axis ; the gibbous, lobe- 

 less glabella overhanging the front margin ; large remote depressed eyes ; rounded pleurae ; 



' In former pages I have used Dalman's old term hypostome for the incurved under front margin of 

 the head, which supports the labrum ; and I adhere to this, although the term epistome is often adopted. 

 Barrande calls it 'la doublure frontale.' 



2 Better defined and restricted by Angelin, 1852. 



