96 SYSTEMATIC ARRANGEMENT 



Asaph, selenurus, Green {Mon. 46), Eaton {Geol. TcrZ-iJooA, 31), Harlan [Med. and Phys. Research. 

 302), Milne Edw. [Crust, iii, 309). 



Asaph, laticosiatus, Green [Mon. 45). The caudal shield resembles that of Ph. conophthalmus 

 (No. 6), and may possibly belong to Ph. odontocephalus , or to a similar species ; it has twelve short 

 joints in the rounded caudal axis, and nine lateral ribs, of which the two last run towards the obtuse 

 end-points. 



Asaph, myrmecoides, Green [SiU. Joiirn. vol. xxxii, p. 397), Harlan [Med. and Phys. Res. 303), 

 still more resembles the caudal shield of Ph. conophthalmus, being equally short, broad, and diverging 

 at the end, but it is much larger, being upwards of three inches in width. The obtuse, but comparatively 

 not very broad axis, consists of from seventeen to eighteen rings, and on the sides we remark thirteen 

 ribs ; both are covered with large round tubercles. 



Asaph, astragalotes, Green [SUl. Journ. vol. xxv, p. 325), Harlan (/. c), I consider the caudal 

 shield of a large individual of Pliacops latifrons, or Calym. biifo, Green ; it has from seven to eight 

 rings at the axis, and five lateral ribs. 



3. I am equally imable to interpret distinctly Asaph. Powisii, Murch. [Sit. Syst. ii, 661, PI. XXIII, 

 Pig. 9, a, b), which certainly is a decided Phacops, and belongs to the same group, together with Ph. 

 anchiops or Ph. sclerops, but has reraai-kably small eyes. The body appears to me to fit but little to 

 the cephalic shield, the rings are much too broad towards the margin of articulation of the cephalic 

 shield. According to Emmerich [Leonh. and Bronn, Jahrbuch. 1845, p. 53), the head is identical with 

 Ph. sclerops (No. 4) ; according to Portlock, on the other baud [Rep. of Geol. 297), the body belongs 

 to Asaphus.* 



Suh-grmip [d). The caudal shield having long spines on its whole circumference. 



13. Ph. urachnoides .- Scuto capitis in medio marginis antici acuto, angulis posticis valde productis; 

 limbo scuti caudalis decies spinosa. Long. 1-1 ^i". Tab. IV, Fig. 7. 



j{,ef. — Asaph, arachnoides, Goldf. Leoiih. and Bronn sn. Jahrb. 1843, 561. 13, Tab. V, 

 Fig. 3. Paradox, gratet , Rom. Verst. d. Hertz. 39, Tab. XI, Fig. 11. Pleuracanthits 

 pimctatus, Rom. Rhein. TJberg. 82. Olenus pimctatus. Steinung, Mem. de Soc. Geol. 

 Fr. i, 356. Honinghaus, Epist. Cref. 1835. Emmr. Dissert. 55. Plenra- 

 canthus arachn. Milne Edw. Cnist. iii, 329. 

 Lqc_ — In an ash-gray limestone of the Eifel, according to specimens in Honinghaus's 

 and Sack's collections. 



Cephalic shield oblong, parabolic, the centre of the anterior margin pointed, and 

 rather curved upwards ; the anterior lobe of the head very large, the three following suc- 

 cessively smaller; eyes high, strongly arched, exactly equalling the length of the three 

 posterior lobes of the head, each single eye furnished with 162 lenses; posterior angles of 

 the cephalic shield very much lengthened, reaching as far as the ninth ring of the body. The 

 latter gradually becomes rather broader as far as the fifth, afterwai'ds again more narrow ; 

 the lateral lobes considerably broader than the rings, and lengthened at the end into a spine, 

 which at each successive joint is larger than at the preceding. Caudal shield parabolic, 

 rather flattened ; the axis slender, thirteen-jointed, the sides furnished with five elevated 

 ribs, which issue from the arched circumference, and at each side five spines, which become 

 shorter from the anterior to the posterior part, and correspond with the ribs ; the first 



* The head and tail figured by Sir Roderick jNIm-chison, under the name of Asaphus Powisii, are 

 now known to belong to difi'erent Trilobites. The name Asaphus Powisii is retained for the tail, whilst 

 the head is the cephalic shield of a Pliacops, named by Mr. Salter, who has met with the tail of tlie 

 species, Phacops felinns. — Ed. 



