Skenea. MOLLUSCA. PECTINIBRANCHIA. 313 



2. D. nodosa — Upper side with a nearly central ridge ; under side with a 

 row of rather large nodular projections ; aperture nearly round. — Euompha- 

 lus nodosus, Sower. Min. Conch, t. xlvi. — Carboniferous Limestone, Derby- 

 shire. 



3. D. discors — Whorls three or four, above subimbricated, with four spiral 

 projections ; beneath concave, smooth.— Euomphalus dis. Sower. Min. Conch, 

 t. lii. f. 1 — Carboniferous Limestone, Colebrook Dale. 



4. D. rugosa.— Above imbricated, with four spiral projections; beneath 

 plaited ; margin rather acute — Park. Or. Rem. iii. 77- t. vi. f. 7, 8 Euom- 

 phalus rug. Sower. Min. Conch, t. lii. f. 2. — Carboniferous Limestone, Cole- 

 brook Dale. 



5. D. angulosa — Above subimbricated, with three spiral projections ; be- 

 neath striated, with five obscurely plaited spiral projections ; aperture ob- 

 scurely octangular Euomphalus ang. Sower. Min. Conch, t. lii. f. 3.— Car- 

 boniferous Limestone, Benthall Edge. 



6. D. tuberculata — Discoid, whorls striated spirally and transversely, with 

 a row of transverse tubercles on each side— In Carboniferous Limestone, West 

 Lothian. 



Gen. CIRUS. — Spire produced. 



1. Leachii. — Longitudinally striated ; whorls many, with several rows of 

 tubercles crossed by numerous small ridges ; upper row of tubercles spiri- 

 form, compressed— Sower. Min. Conch, t. ccxix. f. 3 Under Oolite, Dundry. 



2. nodosus. — Conical, acuminated, or discoid, with an acuminated spiral 

 umbo ; spire reversed ; whorls many, with two rows of longitudinally ex- 

 tended tubercles, crossed by numerous small ridges Sower. Min. Conch. 



(cast) t. cxli. f. 2. and t. ccxix. f. 1, 2, 3 Under Oolite, Dundry. 



Gen. LV. SKENEA. — Spire depressed, and destitute of 

 spinous processes. 



264. S. depressa. — Whorls three or four, wrinkled across, 

 with a deep groove for the separating line. 



Serpula cornea, Adams, Linn. Trans, v. v. t. i. f. 33. — Helix depressa, 

 Mont. Test. Brit. 439, t. xiii. £ 5 — At the roots of fuci, common. 

 Breadth one line ; colour brown ; whorls round ; beneath, a large central 

 cavity exposing the upper volutions ; above, the whorls are nearly on a level, 

 their central edge bending suddenly at the separating line, and forming a 

 deep groove ; the transverse lines of growth are irregular and rough; aper- 

 ture circular, detached from the body-whorl, sometimes slightly reflected. 



265. S. serpuloides. — Whorls three, white, smooth, and 

 glossy. 



Helix utrinque umbilicata apertura rotunda unici anfractus, Walk. Test. 

 Min. 7- t. i. f. 26. (the fry) — Helix serp. Mont. Test. Brit. Sup. 147. 

 t. xxi. f. 3. — Not uncommon from deep water. 



Breadth about ' l5 th of an inch; subopake; whorls round, nearly on a level 

 above, with a deep separating line ; beneath, with a central cavity, round 

 which there are traces, under a high magnifier, of diverging lines of growth ; 

 aperture circular, with the margin a little reflected. 



