676 
Proceedings of Royal Society of Edinburgh . [sess. 
This species approaches Melosira sulcata forma coronata, Grun. 
(Van Heurck, Syn. Diat. Belg ., ph xci. fig. 24). 
Habitat. — Oamaru deposit (Grove and Sturt !). 
P. interruptus. Grove and Sturt {Jour. QueJc. Micr. Cl. , 1887, 
p. 67, pi. v. fig. 8) has been found by Mr H. Morland {Jour. 
QueJc. Micr. Cl., 1887, p. 167) to be the opposite valve of Cras- 
pedoporus elegans , Grove and Sturt {ibid., 1887, p. 64, pi. v. fig. 6; 
Rattray, Jour. Roy. Micr. Soc., 1888, p. 919). 
Artificial Key. 
' Yalves irregularly conical, with transversely truncated 
extremities, the opposite valves of a frustule of 
unequal heights, 
Yalves elliptical. Markings decreasing rapidly out- 
, j wards, around central space 4^, at border 10, in 
•01 mm., ........ 
Yalves rhombic. Markings increasing gradually out- 
wards, towards central space 6 to 6|, towards 
border 4 to 4 J in ’01 mm., . ... . 
.Yalves circular or subcircular, ..... 
2 . 
f Surface slightly convex ; interspaces large around 
| central space, ....... 
-! Surface almost flat to marginal band. Markings 
papilliform. Processes hour-glass-shaped, 
L Surface dome-shaped, ...... 
o f Markings distinctly fasciculate, .... 
' \ Markings non-fasciculate, 
'Spines robust, conical, interfasciculate, forming a 
circlet at about g of distance between central space 
and edge of valve. Markings areolate, 7 in 
4. - - 01 mm., . 
Spines absent. Markings obtusely angular or sub- 
areolate ; around central space 6, near border 10 to 
l 12, in ’01 mm., 
f Markings areolate, increasing slightly to about semi- 
I radius, thence decreasing similarly to border; 
- J around central space 4J, at semiradius 3 to 3£, in 
' j ’01 mm. Spines absent, 
j Markings towards central space 4|, near border 8, in 
l '01 mm., sometimes with long spines, . 
conicus. 
oblongus. 
Stolterfothii. 
2 . 
major. 
hirsutus. 
3. 
4. 
5. 
spiniferus. 
elegans. 
splendidus. 
nitidus. 
THAUMATONEMA. 
Grev., Trans. Micr. Soc. Lond., 1863, p. 76. — Concatenate, 
discoid. Surface flat, or rising but slightly from centre for \ 
to f of radius, thence sloping steeply downwards to edge of 
girdle and slightly concave at middle of outer portion. Colour 
