MILIOLIDA. 19 



General characters. — Numerous short, subcyliiidrical chambers, forming a long huear 

 shell, of variable dimensions, truncate at one end, and perforated with either a single 

 (often dendritic) aperture, or with several pores ; and at the other (first-formed) end 

 curled into a little crook or knob : this, when small, is often broken off, leaving a tapering, 

 awl-shaped, striated shell, delicate in shape and white in colour. 



8p. cylindracca is common in the Mediterranean, Red, and Indian Seas. We have it 

 small and veiy rare from the Crag of Sudbourne (specimen lost). 



nnicli confusion in the nomenclature ; and it will be useful here to point out some of the best-marked 

 forms of Peneroplis and its varieties, in chronological order : — 



1775. Nautilus pertusus, Forskal (type: comprising broad and narrow varieties). Peneroplis 



pertusus, Forsk. 

 1781. — KKCTVis, Spengler (}iic\\id\ng& vaxiet^ oi Articulina). 

 1785. — UJIBILICATUS, Linni (flat, curled like a crozier-head). Peneroplis U7nbilicatus, 



Linn. 

 1785. — SEJiiLiTUUS, Li7inii (flat, with crozier-head and short stem). Peneroplis 



semilitvus, Linn. 

 1788. — LiTUUS, G»ie/m (long, slender, cylindric, with one end curled). P . {Spirolina) 



lituus, Gni. 

 1791. — (LiTUUs) ARIETINUS, Batsch (narrow, flat, curled at end). P. arietinus, Batsch. 

 1791. — — AClCULAEls, Id. P. {Spirolina) lituus, Gm. 



1803. — PLANATUS, Fichtel and Moll, (broad forms). P. planatus, F. and M. 



1804. Spirolina (Spirolinites) DEPRESSA, XamarcZ: (two subvarietal forms ; one nearly lenti- 



cular, Bendritina ?). P. pertusus, Forsk. 

 1804. — — CYLINDEACEA, /<^. (long, sub-cyliudrical, With one end curled). 



P. {Spirolina) cylindracea. Lam. 

 1808. Peneroplis lanatus, Montfort. P. planatus, F. and M. 

 1816. Cristellaria planata, Ce. dilatata, Lamarck; and 1822, Cr. souamula. Lam. 



P. planatus, F. and M. 

 1826. Dendritina arbuscula, D'Orb. (lenticular). P. {Bendritina) arhuscula, D'Orb. 

 1839. CosciNOSPiRA (Spirolina) Hemprichii, Ehrenberg (stout, cylindric, with boldly curved 

 end). P. {Spirolina) cylindracea, Lam. 



Although Forskal did not figure P. pertusus, yet there can be no mistake in regarding the following 

 escription as especially belonging to it (' Descript. Anim. Itin. Orient.,' 1775, p. 125) : "Having com- 

 ressed whorls, transversely sulcated, and marked with slight longitudinal striae ; at the aperture per- 

 forated with pores. Colour snow-white Whorls straight at the base [top], often dilated, some- 

 times linear ; at the apex [earliest part] convolutely spiral." It was from Suez, Red Sea. 



