STROPHALOSIA. 41 



overlooked or unobserved by those who have described the interior of this species, as they 

 are not represented in any of their illustrations. These impressions are also much less 

 deeply marked in Strophalosia than in Productus, but prove that they were in general 

 character essentially similar to those of that genus, varying only to a small extent in shape 

 and depth. 1 The position of the adductor in this valve has been noted by several 

 writers, and is represented in pi. xii, fig. 3, of Professor King's ' Monograph ;' but the 

 author describes them "as the cardinal and valvular muscular scars confluent," which 

 appears to be a mistaken view from the evidence afforded by my specimen, in which both 

 are distinctly separated, as in Productus. 



In the interior of the smaller or dorsal valve the cardinal process is of moderate dimen- 

 sions, but considerably developed and produced in certain individuals (figs. 12, 16, 17), 

 from the base of each of which proceed three strong ridges, viz., a median longitudinal one, 

 which extends to about half the length of the valve, and two short lateral ones, which 

 constitute the inner socket-walls. On either side of the median ridge or septum there 

 are two small longitudinally divided pear-shaped impressions, produced by the adductor, 

 the one close to the central ridge being the largest (figs. 8 and 12 a). The reniform 

 impressions are large, their prominent outer edge issuing from between the adductor scars, 

 gradually arch forwards and outwards on each side, then turning backwards for about half 

 their length, and finally run inwards horizontally to meet each other near the extremity of 

 the median septum or ridge. The interior surface of this valve is either uniformly convex, 

 or presents a small medial depression or sinus towards the front (fig. 12), while in a few 

 young individuals there is a raised margin, somewhat similar to that seen in different 

 forms of Thecidium, and of some other Brachiopoda (fig. 17 2 ). The internal surface is 

 also minutely pitted all over, with the exception of those parts occupied by the muscular 

 scars. 



Strophalosia Goldfussi is stated by Professor King and Mr. Howse to have been found 

 in the compact and shell limestone of Humbleton and Tunstall hills, Clack's Heugh, 

 Ryhope-field House, Dalton-le-Dale, Garmundsway, Castle-Eden Dene, and in the Breccia 

 of Tynemouth. 



On the Continent it seems equally common. Count Minister's original example was 

 obtained from the lower Zechstein of Ropsen, near Gera. Dr. Geinitz mentions Milbitz, 



1 The muscles were, perhaps, stronger and more deeply implanted in Productus, to supply the defi- 

 ciency of the articulated hinge which Strophalosia possesses. The cardinal process appears to be also 

 rather larger in Productus than in the last-named genus. Mr. Howse observes, that " the boss or cardinal 

 muscular fulcrum (in Productus) when in situ, fills nearly the whole of the umbonal cavity of the lower 

 valve, and presses against its inner surface ; it may thus assist in keeping the valves in position." 



2 I have been able to study this curious peculiarity in four or five examples from Tunstall hill, in the 

 collection of Mr. Howse. They consist of beautifully preserved detached valves of young individuals, not 

 exceeding three and a half lines in length ; but in all the larger individuals which have come under my 

 observation, the raised margin has either entirely disappeared, or exists only in a very obscure and rudi- 

 mentary condition. 



6 



