EXPLANATION OF THE PLATES. 



All the figures are of natural size unless the amount of enlargement is stated. 

 Owing to the very great difference between the coarse and fine species I have 

 found it impossible to make all magnifications of details the same. The magni- 

 fications are all 2, 5, 10, or multiples of 10, and when possible a 10 magnification 

 is given for comparison. 



PLATE I. 



Figs. page 



1 — 4. Gonularia linnarssoni, Holm Mrs. Gray's Collection . . 16 



1. Specimen from Llandeilo Beds, Balcletchie. Uncrushed, showing a square 



cross-section. X 2. 



2. Small flattened specimen from the same locality. Shell almost smooth, x 2. 



3. Marginal groove, x 20. 



4. Facial groove showing striations. x 20. 



5 — 9. Gonularia asjiersa, Lindstrom . . . .19 



5. Specimen from the Lower Ludlow of Church Hill, showing the apertural 



cone. British Museum (Nat. Hist,), no. 5373. 

 6 a. Large imperfect specimen from the same locality, compressed so as to 



show the "septa" from the under faces. 6 b. Portion of shell with 



"septa." x 5. 6 c. Ornamentation, x 40. British Museum (Nat. 



Hist,), no. G. 4603. 

 7. Ornamentation of another specimen from the same locality, x 40. British 



Museum (Nat, Hist,), no. G. 4604. 



8 a. Specimen from the Silurian of Gotland. 8 b. Ornamentation, x 40. 



Vetenskaps Akademi, Stockholm. 



9 a, b, c. Ornamentation of other Swedish specimens, x 40. 



10 — 12. Gonularia punctata, sp. nov. Mrs. Gray's Collection . . 20 



10 a. Small specimen from the Upper Llandovery of Penkill, uncrushed. 



10 b. Cross-section of shell. 10 c. Ornamentation above fracture, 

 x 20. 

 11. Portion of the inner surface of the shell of another specimen, showing the 

 septa projecting inwards only, x 10. 



12 a. Ornamentation of a larger specimen, x 20. 12 b. External cast of 



the same, x 20. 



13, 14. Gonularia sp., cf. aspersa, Lindstrom Mrs. Gray's Collection . 21 



13 a. External cast of large specimen from the Starfish Bed (Upper Bala), 



Grirvan, showing one face. 13 b. Ornamentation, x 20. 



14 a. Ornamentation of a small specimen from the same locality, x 20. 



14 b. The same, x 40. 



