32 ACANTHOCfflTES-NOTOPLAX. 



The type of 3IacanclreUus is not 31. costatus Ad. & Ang., as stated 

 by Dall in Proc. U. S. Nat. Mus. 1878, p. 299, but if. p lume us C])r., 

 teste Dall, I. e. 1881, p. 288. The first use of the name, being 

 unaccompanied by a diagnosis, will fall. At the time Carpenter 

 established the group for M. jjlumetis, he had never seen the species 

 codatus. 



A. sPEciosus H. Adams. PI. 1, figs. 23, 24, 25, 26. 



Shell elongated ; valves acutely heart-shaped, olivaceous maculated 

 with brown ; each valve with a wide, smooth dorsal ridge, the side 

 areas coarsely granulose, the lateral area indicated by a raised line. 

 Girdle brown, spinulose ; pores moderate sized, encircled by con- 

 spicuous spicula. 



Length 72, breadth 24 mill. (H. Ad.) 



Tasmania (Mus. Cuming) ; Flinders Island (Jos. Milligan.) 



Cryptoplax (Notoplax) speciosa H. Ad., P. Z. S. 1861, p. 385, 



This species resembles A. exqimitus Pils. in the narrowness of the 

 exposed portion of the valves, but in typical specimens of that form 

 the tegmentum is decidedly narrower. In A. 1iemp)liilli Pils. from 

 Florida, which is a Notoplax in its apparently separated valves and 

 denticulate tail-plate, the spcciosus differs in the longer, narrower 

 tegmentum, etc. 



The figures of my plate were drawn by Mr. E. A. Smith from the 

 types. Carpenter gives the following useful notes on the specimens 

 in the British Museum : The lateral areas are distinctly marked 

 off" by larger granules along a raised diagonal line. The mucro of 

 the posterior valve is raised, at an angle of about 160°, and situated 

 at the posterior third of the tegmentum. The jugular areas are 

 both smooth and raised ; the scales of the sides are also smooth flat 

 and raised. The girdle is entirely covered by a dense mass looking 

 spongy, but consisting of spicules of moderate length and extremely 

 crowded. There are consj)icuous pores but the hairs in them are 

 not longer than the rest, and therefore it is difficult to distinguish 

 them. The sinus is very narrow and deep. Slits all very short. 

 The anterior valve has grooves with raised edges extending from 

 eaves to the slits. Posterior valve having side slits, situated as in 

 Acantliochites, but the posterior plate is j)i"etty regularly grooved 

 radially, so as to crenate the margin, almost amounting to little nicks 

 from slit to slit. 



