106 



SYNOPSIS OF THE CHARACTERS OF THE 



valve form two large, irregular, oval cicatrices in the ventral valve, situated one on eacli side, about midway 

 between the central septum and the lateral margin of the shell, and about their own length distant from the 

 anterior margin ( see fig. 9, the ventral valve of the Producta pustulosa, B b) ; e E (fig. 9) shews the origin 

 of the second pair of adductor muscles, forming small, pear-shaped cicatrices, close to the centi'al septum, the 

 lower, dilated portion curving outwards. The ventral valve is connected to the dorsal, by a kmd of cardinal 

 tooth, usually notched (see fig. 10, b), similar to that of Thecidea. There is in Fig. 9. 



the centre of the ventral valve of all the species, a long, prominent, shelly, septum ? 



arising from the cardinal tooth, and extending to withm a short distance of the 

 anterior margin ; it increases in prominence towards its anterior end, where it is 

 abruj^tly trimcated or rounded according to the species ; it is in some measure ana- 

 logous to the central septum, in the dorsal valve of the Spirifers. The beavitiful 

 markings, represented fig. a a, may be viewed as a modification of the spiral appen- 

 dages of Spirifer ; they are in fact the support for the arms of the animal, but in- 

 stead of their extremities being free, and projecting into the cavity of the .shell, as 

 in Terehratida or Spirifer, it is fixed along its whole length to the surface of the 

 ventral valve, as we see in Thecidea and Crania; the reason of this difierence appears 

 to be that Spirifer and Terehratida, having convex ventral valves, and being at- 

 tached so as to hang by the beak, their arms are so placed, that the bases of the cones which they form, when 

 retracted, become parallel, and their extremities, when unrolled, extend in the direction of the anterior margin 

 of the valves, the supports in that case extending themselves into the centre of the cavity of the shell ; but in 

 these Brachiopods, as Crania, Thecidea, Orhicula, &c., which have the ventral valve flat, the arms are coiled 

 so that their bases rest on its surface, both on the same plane ; the supports, therefore, are always fixed, in their 

 entire length, to the internal face of tlie ventral valve, and project but sHghtly from it. That the arms of tlie 

 Productm were also placed in the same manner, appears evident from the accordance pointed out in the form 

 and mode of attachment of the appendages ; and if so, we would have an important anatomical fact to justify 

 the allocation of the Producta {Athyridce), near Orhicula. 



Producta aculeata. Mart. sp. 



Anomites aculeatus. 3Iartin, Pet. Derb. — Productus aculeatus. Sow. Min. Con. 



Sp. CIi. — Rounded, very gibbous; beaks large, tumid; front slightly indented ; smooth; dorsal valve with 

 irregular, adpressed spines ; ventral valve without spines. 



This species is chiefly remarkable for the curious position of Its spines, which have their points directed 

 towards the beak, appearing, as it were, to force themselves up through the surface of the dorsal valve ; their 

 bases are large, few, and irregularly placed ; the ventral valve is very concave, and has no spines ; excepting the 

 spines on the dorsal valve, the surface is perfectly smooth ; the hinge-line Is exceedingly short. Length five 

 lines, width six lines. 



Producta antiquata. Sow. 



Anomites semireticvdatus. Martin, Pet. Derb. — Productus antiquatus. Sow. Min. Con Productus lobatus. Deshayes. 



Sp. Ch. — Subquadrate; surface with coarse, rough, longitudinal stria;; rostral portion of the shell trian- 

 gular, entirely covered with concentric undulations, which become large and spinous towards the sides ; front 

 of old shells produced subcyHndrical, with parallel sides, which are without stiice, but have numerous, very long, 

 cm'ved spines ; mesial hollow wide ; botli valves nearly alike ; width of the hinge-line equal to the length of the 

 shell. 



This is the most common species of the genus ; Martin's figure, above referred to, obviously represents a 

 yoimg shell of this species, having a flattened, triangular figure, and the entire surface reticulated by the con- 

 centric wrinkles. The same portion has been .figured by Sowerby, in the Alineral Conchology, under the name 



