'66 MISS J. DONALD ON EHABDOSPIEA.. [Feb. 1 898, 



length = 16^ mm., width = 7| mm. The highest whorl appears 

 narrower than it really is, through not being whollj^ preserved. 



Locality and Horizon. — ' Main Lime,' Lower Limestone Series (d^), 

 Braidwood, Carluke. 



Rhabdospira compacta, sp. nov. (PI. V, figs. 5 & 5 <x.) 



Description. — Shell conical, of moderate size, composed of about 

 eight whorls. These are convex, broad, compactly coiled, ornamented 

 by seven strong raised threads, with nearly equal spaces between, 

 and two additional threads below on the bodj-whorl. Sutures 

 rather deep. Lines of growth curved, scarcely sigmoidal, coming 

 almost direct down the whorl. Base convex. Aperture and proto- 

 conch unknown. 



Resemblances. — This species occurs as an external mould in an 

 impure limestone. It bears more resemblance to Aclisina (?)sulcatula, 

 M'Coy, than to any form I know, but the threads with which it 

 is ornamented are more numerous and less strong, also there are 

 not so many fine additional threads on the body-whorl. 



The specimen figured in PI. V, fig. 5, is in the Museum of Practical 

 Geology, London ; it is drawn from a wax impression, and measures 

 10| mm. in length, 4| mm. in width. 



Locality and Horizon. — HoUin Gill, Hawes, Wensleydale. Yore- 

 dale Eocks (d^). 



Family Murchisoniidae^ Koken. 



Genus Muechisonia, D'Arch. & De Yern. 



Section Aclisoides, Donald. 

 (For the synonymy, see p. 67.) 



Description of the Section. — Shell small, elongated, conical, com- 

 posed of numerous whorls. Protoconch smooth, simply coiled on 

 the same plane as the rest of the spire. YV^horls moderately 

 convex, spirally striated. Aperture ovoid, outer lip as indicated 

 by the lines of growth possessing a sinus, towards which the lip 

 retreats above and from which it arches forward below. Base 

 convex. Umbilicus closed. 



Dimensions. — The length of the British species varies from 2 or 

 3 up to 16 mm. ; as none of the specimens that I have seen are 

 entire their dimensions would probably be greater if perfect. 

 De Koninck states that the Belgian forms attain 3 cm. in length. 

 The specimen in the Brussels Museum marked as the type of 

 A. [MurcMsonia'] striatula is only 9| mm. in length. 



Resemhlances. — This section or subgenus may be distinguished 

 from the typical Murchisonice by possessing more convex, bead -like 

 whorls, ornamented by numerous spiral threads, by the filling up 

 of the sinus in the outer lip not giving rise to so distinct a band, 

 for the sinus merely occupies the space between two or three of 

 the ornamenting threads. In this latter particular it is most like 



