176 SALENIA 



latter is much less inflated, the apical disc thinner and more depressed, the ambulacra 

 are straighter, and the mouth-opening wider. 



Locality and Stratiyrap/iical Position. — The specimen I have figured belongs to the 

 British Museum, and was collected from the Upper Greensand near Longleat, Wilts, where 

 it is extremely rare. This species appears to be equally scarce in France ; as it was 

 obtained from the Cenomanian = Upper Greensand, in the " He d'Aix" (Charente-Infe- 

 rieure). From this locality the type specimens in the Musee de Paris and others in 

 private collections were collected. 



b. — Species from the Grey Chalk. 

 Salenia Austeni, Forbes. PI. XXXVII, figs. 1, 2. 



Salenia Austeni, Forbes, MS. Woodward, Mem. Geol. Surv., Decade V, App., 1856. 

 — — Forbes. In Morris's Catalogue of British Fossils, p. 89, 1854. 



Diagnosis.- — Test tumid, more or less elevated ; ambulacra prominent, slightly 

 flexed, two complete rows of remote marginal granules and two incomplete rows of smaller 

 granules within j inter-ambulacra with two rows of tubercles, five in each, decreasing in 

 size from above the ambitus to the peristome. Miliary zone wide, sparsely covered with 

 granules. Apical disc small, thick, prominent ; sutures marked by regular punctuations ; 

 vent elevated, periprocte projecting, having a sharply crenulated border. 



Dimensions. — Altitude, five tenths of an inch ; latitude, seven tenths of an inch. 



Description. — This beautiful Salenia has in general a tumid body, with a narrow base, 

 inflated at the sides, and convex on the upper surface, the vent being very excentric, elevated, 

 and prominent ; in some examples, however, the upper surface is more or less depressed, 

 and approaches the form of S. petalifera. 



The ambulacral areas are narrow, nearly straight, and very prominent ; they have two 

 complete rows of remote marginal granules, twenty-four in each (fig. 1 d), and two 

 incomplete rows of smaller central granules, which occupy two thirds of the area (fig. 1/). 

 The poriferous zones are narrow and slightly flexed ; the pores are very small, oblique, 

 and unigeminal, ten pairs occupying the height of a single plate (fig. 1/andy). 



The inter- ambulacral areas are wide, and regularly developed (fig. 1 a), with two rows of 

 primary tubercles, gradually diminishing in size from the upper to the lower part of the 

 area, those near the disc being large, and those near the peristome small. Pig. 1 e shows 

 an entire area magnified four diameters; the tubercles are seated near the poriferous 

 zones ; each is surrounded by a wide, areolar space, and around the margin thereof three 

 parts of a circle of six to eight large round granules are placed (fig. 1 d, e, y). 



The miliary zone is wide throughout, and sparsely covered with small granules, especially 

 near the discal region (fig. 1 d, e). The base is concave (fig. 1 b), and highly ornamented 



