122 



(;owards the front, whereas the fifth is more round, and directed 

 straight out to the side, and at the same time somewhat up- 

 wards. The first spine belongs to the orbital region, the second 

 and third to the hepatic region, the fourth to the epibranchial 

 lobe, and lastly the fifth to the mesobranchial lobe. 



After the last spines of the anterio-lateral margin comes 

 the posterio-lateral margin, the length of which (12 mm.) far 

 surpasses that of the former margin. It is almost straight, 

 and forms an obtuse angle with the posterior margin. The 

 anterio- and posterio-lateral margins have not, like the anterior 

 margin, a row of regular small tubercles. 



The posterior margin (17 mm. broad) forms a flattened 

 curve, the middle part as well as the side parts are slightly 

 bent inwards. The posterior margin carries throughout its length 

 a row of quite small regular tubercles. 



The furrows which border the different regions of the cara- 

 pace are shallow, but yet rather distinct. In the casts they 

 are seen most distinctly; on weathered shells it is sometimes 

 somewhat difficult to follow their course. 



From the incurvation between the two middle of the 

 four front spines , runs a small flat furrow which divides 

 the front into two symmetrical parts. Farther back, where it 

 separates the two epigastric lobes, it gets deeper and broader^ 

 and then it divides itself into two branches which between them 

 enclose the long forward extension of the mesogastric lobe. The 

 epigastric lobes are seen as a small, crooked, square promi- 

 nence on either side of the furrow; by another furrow they 

 are separated from the elevated part of the supraorbital margin. 



Between the epigastric and protogastric lobes a broad, flat 

 furrow is found. The last mentioned lobe is large, and rather 

 flat, its highest part is near the furrow which separates it from 

 the long mesogastric lobe. 



The metagastric lobe has grown together with the meso- 

 gastric lobe, and forms with the latter a hexagonal, slightly 



