CEPHALASPID^. 21 



Derivation. — Named after Mr. Lloyd, of Whitbach. 



Characters. — Scutum ovatam, parte anteriore latiore quam parte posteriore ; postice 

 sub-acute terminatum, antice margine lato, curvato; lateribus aliquanto depressis et 

 inflectis ; superficie externa striis regulariter ornata prseter superficiem marginis anterioris 

 striis paucis eccentricis notatara ; superficie interna laevi, duobus colliculis obliquis antice, 

 et rugis lateralibus notata. 



Stratigraphical Position. — Lower Old Red Sandstone (Cornstones). 



History. — This is one of the species determined by Professor Agassiz. One of the 

 type specimens figured by the distinguished Ichthyologist is a very good representative of 

 the form (PI. I, fig. 5) ; tbe other (fig. 10) is a broken, distorted specimen: neither of 

 them show the surface-markings or substance of the shield. The specimen drawn in 

 fig. 9, which is a young and somewhat flattened example of this species, was described by 

 Professor Agassiz as Cephalaspis Lewisii, the specific name being in honour of Mr. Lewis, 

 of Ludlow. I have no doubt that the specimen figured belongs to the species Sc. LJoydii. 

 It is quite possible that Professor Agassiz may have meant to include some other form 

 with that he figured under the name C. Lewisii, but there is nothing in the text of his 

 work which tends in any way to explain his views more clearly. The specific name 

 " Lewisii " is a synonym of Lloydii, and has been applied by the local and other geologists 

 to a distinct form of Scaphaspis, which must henceforth receive a new name. 



General Bemarks. — Scaphaspis Lloydii is one of the commonest species in the Corn- 

 stones of Herefordshire and Worcestershire, and is generally obtained in a better state of 

 preservation as regards its form than others of the section. It is, however, rare to obtain 

 a specimen showing the surface of the shield at all satisfactorily. The largest specimens 

 I have seen measure from three to three inches and a half in length, and one and three 

 quarters of an inch in breadth at the broadest part of the shield, which is about the 

 middle. Specimens of from two to two inches and a half in length are more common, 

 but are usually more crushed and imperfect than the larger ones. The outline of the 

 scute presents a most striking similarity to that of a perfect " Cuttle-bone " of the common 

 Sepia officinalis. The form is that of a true ovoid, with the broader cm^ature in front ; 

 the egg-like outline is, however, slightly modified by a depression of the sides of the 

 shield along the narrower portion of the ovoid, which appears as though flattened out and 

 slightly produced along its posterior lateral margins. This, I believe, is caused by the 

 growth of the shield, since it is not nearly so apparent in small as in large specimens. 

 An examination of the internal casts, some beautiful specimens of which are figured in 

 the Plate, shows a few well-marked, broad furrows, corresponding to fainter depressions 

 on the surface of the scute, which mark out regions of difiering convexity on that 

 surface. These lines appear to be caused by variations in the process of calcification 

 of the shield by the thickening of its margin, and subsequent regular increase; somewhat 

 in the same way as ridges are produced in the shells of Brachiopoda and Laraellibranchiate 

 Molluscs, if it is allowable to compare so dissimilar structures. They distinctly trace out 



