Skenka. MOLLUSCA. TECTINIBRANCHIA. 313 



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

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

 liis nodosus, Soiver. Jlin. Conch, t. xlvi — Carboniferous Limestone., Derby- 

 shire. 



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



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

 t. 111. f. 1 Carboniferous Limestone., Colebrook Dale. 



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

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

 phalus rug. Sotver. Min. Conch, t. Iii. f 2. — Carboniferous Limestone, Cole- 

 brook Dale. 



5. D. angulosa Above subimbricated, with thi'ee spiral projections ; be- 

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

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



boniferous Limestone, Benthall Edge. 



6. D. tuberculata Discoid, whorls striated spirally and transversel_r, with 



a row of tra^sverse tubercles on each side — In Carboniferous Limestone, West 

 Lothian. 



Gek. 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. f. 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. serpulokles. — Whorls three, white, smooth, and 



glossy. 



Helix utrinque umbilicata ajiertura 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 \ gth 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. 



