THE FAUNA OF THE ST. JOffiST GEOtTP. 16S 



work done by the Swedish and Norwegian palaeontologists who followed Angelin in the 

 study of the fauna of the Paradoxides beds. By their careful and thorough examination of 

 the sections in the field, and by their faithful and voluminous descriptions of the characters 

 of the species, as well as by their zoological acumen, they have laid students of this 

 fauna under deep obligations ; and have built up a store of knowledge of the characteris- 

 tics of these early forms of life such as has been done in no other country. 



Explanation of Plates. 



Plate I. 



Fig. 1. — Ayraulos WIdtJiddianm, n. ap^^a, Narrow form, middle piece of the liead-shield. Jlag. ';. — h, Same seen in 

 profile. — c, Same seen in front. — d, Same, part of broad form. Mag. t. — e, Same seen in profile-—/, Same 

 seen in front.— 3, Var. compressa, same part of head-shield. Mag. }. — h, Same seen in profile. — i, Same 

 seen in front. All from Div. Ic'. St. Martin's. See p. 130. 



Fig. 2. — Agraulos HoHiiimtx, n.sp.— a. Middle piece of head-shield of narrow form (mould) 13 mm. Natural size. — 

 h, Same seen from the side.— e, Same seen in front— d, Same, part of head of broad form (mould) 10 

 mm. Mag. IJ.— c, Same seen in profile.—/, Same seen in front.— g to m, Embryonic and larval stages. 

 g, Embryonic head-shield, li mm. Mag. •"i".— A, Embryonic head-shield, IJ mm. Mag. ].—i, Larval, 

 mould of a head-shield, 2J mm. Mag. 'i—k, Larval, head-shield, broad form, .5 mm. Mag. ?.- m, Larval, 

 mould of head-shield of narrow form, 5 mm. Mag. ?. All three heads are from Div. Ic-, at Portland 

 and St. Martin's. See p. 1S3. 



Fig. 3.—LiostracMs tmer, Hartt.— o. Complete example of the narrow form. Natural size. From Div. l.c'. Portland 

 —h, Head-shield of variety. Natural size. From Div. Ic', at St. Martin's.— c. Middle piece of head and 

 part of thorax of broad form. Natural size. From Div. Ic'. Portland. See p. 137. 



Fig. i.—Lioslracvs Ovangondianvs, Burtt., middle piece of head-shield, broad form, 12 x IG mm. Natural size.— 



a, Movable cheek, 4 x 11 mm. Natural size.— 5, Var. immarginata, middle piece of the head-shield. 

 11 X 14 mm. Natural size— c, Same in profile.— cf. Same seen in front. All the above are from Div. l.c"; 

 Portland.— c, Var. plana, middle piece of head-shield, 8 x 10 mm. Mag. î.— /, Same in profile.— 3, Same 

 seen in front.— 7i, Var. gibha. Middle piece of the head-shield, 7i x 9 mm. Mag ?.— v. Same in profile.— 

 k, Same in front- These two vars. are from Div. Ic'. St. Martin's. See p. 138. 



Plate II. 



Fig. l.—Ptychoparia lAmmrsnoni, Brôgger.— a. Middle i)iece of head-shield, broad form, 10 x lU mm. Mag. t.- 



b, movable cheek, 2 x 8J mm. Mag. =f.— c. Movable cheek, shewing tubercles, 2x8 mm. Mag. f— 

 d, Pygidium of broad form, 2 x 4J mm. Mag. ?.— e, Pygidium broad form, shewing two pairs of tubercles 

 on rachis, 2^x6 mm. Mag. ?.—/-n, Embryonic and larval stages. /First embryonic stage with con- 

 tinuous glabella and the pygidium outlined, J x | mm. Mag.^'^— ff. Second embryonic stage with con- 

 nuous glabella and the pygidium, etc., defined, } x J mm. Mag. '-f.—h, Third embryonic stage, head- 

 shield only, glabella nearly continuous, ocular lobes appearing, 1 x IJ mm. Mag. 1 . — i, Same seen from 

 the front— A-, Fourth stage. Glabella shortened, anterior fold and occipital spine distinct, IJ xlj mm. 



Mag. ?. 1, Fifth stage, centre-piece of the head-shield. Glabella still cylindrical, but eyelobes indrawn 



and posterior angles extended, 2 x 2^ mm. Mag. i— m, Sixth stage. Glabella shorter and somewhat 

 conical, 3 x 3J. mm. Mag. t.— n. Half-grown trilobite with narrower front than the adult, 5x6 mm. Mag. 'j. 

 All from Div. Id, St Martin's. See p. 143. 



