C. LapiDorth — On Scottish Monograptidce, 321 



to the concave margin of the periderm, without overlap ; conical 

 in form ; outer margin slightly convex, apertural margin deepl}^ 

 concave, and normal or somewhat everted. 



The hydrothecas in the adult portion of the polypary are broad 

 CU23S, nearlj^ as wide as long, and with large and strong!}^ everted 

 apertures. Fragments from this extremity would be unhesitatingly 

 assigned by most palasontologists to M. Hisingeri, Carr. {^Sagittarius, 

 His., of authors). The proximal portion of the polypary again 

 greatly resembles that in M. Nilssoni, Barr., and it would at once 

 be referred to that species. 



The characters afforded b}^ the hydrothecfe of the proximal end, 

 when carefully noticed, are perhaps sufficiently distinctive. Their 

 outer margins are often somewhat convex, while the apertural edge 

 is invariably deeply concave, and the pointed denticle thus formed 

 is very different from the almost rectangular denticle in If. Nilssoni. 



I regard, however, the separation of this form as a distinct species 

 as merely provisional. A better acquaintance with Monogr. Nilssoni 

 may prove that the distal extremity of that form is provided with 

 the large cup-like thecas of Ilonograptus concinniis. 



Locality. — Birkhill Shales of Dobbs Linn, Belcraig, Garple, etc. 

 EXPLANATION OF PLATE X. 



Fig. 1. Eastriles peregrinus, Barr., magn. ; showing the distal prolongation of 



the virgula. Coal-pit Bay. (Coll. W. Swanston, Esq.) 

 ,, 2a — b „ distans, Lapw., nat. size. Meigle Hill, Selkirkshire. 



„ 3. ,, Linncei, Barrande ; Grapt. de Boheme, plate iv. fig. 2. 



,, 4« — b ,, capillaris, Carr., 4«. nat. size ; 46. magn. DufFkinnel. 



,, 5. ,, peregrinns, Barr., var. hybridus. Belcraig Linns, Moffat. 



,, 6« — d Cyrtograptus Carruthersi, Lapw. ; 6«. proximal portion ; Qb. primary 



branches ; &d. magn. Elliottsfield, Eoxburghshire. 

 „ la — e Monograptus Nilssoni, Barr. ; 1c. proximal extremity ; la. adult 



portion; lb. magn. Leintwardine. (Coll. Prof. H. A. 



Nicholson.) 

 ,, 8rt — b ,, Salteri, Geinitz ; 8a. nat. size. ; 8b. magn. Caddonwater 



Head, Selkirkshire. 

 ,, 9a — d ,, attemuitus, Jlo-pk. ; 9^. magn. Dohhs Linn, and Riskinhope 



Burn. 

 „ 10« — e „ intermedius, Carr., lOi?. magn. Duffkinnel, Dumfriesshire. 



(CoU. Prof. H. A. Nicholson.) 

 ,,11 ,, intermedius, var. involutes. Dobbs Linn. 



,, I2a — e ,, gregarius,JjSi-pw.; 12a. nat. size; 126. magn. ; 12c. proximal 



extremity showing sicula. Dobbs Linn. 

 5, 13a — e „ argutus, luai^w. ; 13a. proximal extremity, 136. adult portion, 



13c. magnified. Dobbs Linn, Dumfriesshire. 



EXPLANATION OF PLATE XI. 



Fig. la — e Monograptus eoncinnus, Lapw. la. distal portion; 16. magn.; Ic. 

 central portion ; Id. do. magn. ; le. proximal portion. Dobbs 

 Linn. 

 2a — e Monograptus Sandersoni, Lapw. 2a. b. distal portions ; 2g. d. do. 



magn. ; 2e. proximal end. Dobbs Linn. 

 Za — n Monograptus tenuis, Portlock sp. 3«. b. c. adult portions ; Zd. e. 

 do. magn.; 3/. g. proximal extremities ; 3 h. k. do. magn. Dobbs 

 Linn and Ettrickbridgend. 3^. m. n. Irish examples. Limehill, 

 Pomeroy, Tyrone. 

 In these Plates the figures in black are of the natural size. Those in outline are 

 magnified ; reduced to a uniform scale of five diameters from drawings made with 

 the camera lucida. 



DECADE II. — VOL. III. — NO. YII. 21 



