60 G. F. MATTHEW: ILLUSTRATIONS OF 



apices, aud may have led to the impression that the apex was central ; in very young shells, 

 the elongation of the layers over the front of the shell gives it a narrowly elliptical form 

 like Parmophorus (but there is no sulcus in front.) 



The internal features of this shell would indicate that its modern relatives are to be 

 found among the Fissurellidœ. The muscular impression as observed in an immature 

 individual, is horse-shoe shaped, elongated and directed away from the apex ; the arched 

 end is attenuated and somewhat hexagonal in outline. The space within is divided into 

 two areas, of which the inner is lozenge-shaped posteriorly, where it encloses the apical 

 ridge ; and constricted anteriorly, where it comes opposite the enlarged limbs of the mus- 

 cular impression. Outside of the muscular impression, faint concentric striœ impi-ess the 

 inner surface of the shell. 



Except for the absence of an involute apex this shell is not unlike Carinaropsis car- 

 inata, Hall, of the Trenton formation ; ' it is compressed near the apex, and expands 

 rapidly toward the aperture in a manner similar to that species, but in the way in which 

 the concentric ridges are added it is comparable rather with Mefoploma (?) rugosa ; our 

 shell, however, is not a Metoptoma, as it is not truncated on the side beneath the apex 

 after the manner of the Carboniferous genus so named. 



Parmoi)horella lived in the shallow seas near the coast, if one may judge from the 

 species of other genera associated with it, and probably was a bottom-crawler. The true 

 Stenothecœ appear to have been more varied in their habit of life : they have not only been 

 found in company with Parmophorella, but also in the fine shales where remains of sea- 

 weeds (?), sponges, hydrozoa, etc., are met with. A fact in reference to the variation of 

 resembling forms like these is related by Woodward,^ who mentions several wide limpets 

 which assume a narrow compressed form when growing on seaweeds. 



Length, i.e. height from apex to middle of the orifice, •? mm. Width, i.e. length of the 

 aperture, 12 mm. ; width of the aperture, 11mm. 



Horizon and Locality. In the calcareous conglomerate (l.c') and the grey shales (l.r) of 

 Div. l.c at Portland and Hanford Brook, St. Martin's ; also in the grey shales (l.r) at Eat- 

 clifiF's Stream, Simonds, and at Hanford Brook, St. Martin's. Common. 



HARTTIA, Walcott. 



Haettia Matthewi, Walcott. (Plate V. Fig. 10.) 



IT. S. Geol. Surv., Bull. 10, p. 19, PI. I. Fig. 3. 



This unique little shell was described by Mr. "Walcott in the following terms : — 



" A small oval patelliform shell, having a low, broad ridge, originating on the poste- 

 rior (?) side of the interior, that supports a subcordate shield-like expansion, which 

 extends out over the anterior (?) portion of the interior when we look down into the shell. 

 The broad base of the ridge, and the general character of the shield-like extension are 

 well shown in the figure. 



" The character of the apex is unknown, as the only representation of the genus and 



' J'alœontology of N. York, i. 183, PI. 40, fig. 1. ' Manual of the Mollusoa, p. 280. 



